diff --git a/ckeditor.html b/ckeditor.html
index e123264..5b57252 100644
--- a/ckeditor.html
+++ b/ckeditor.html
@@ -22,21 +22,4 @@
         })
     </script>
   </body>
-
-  <style>
-    .bes-online-editor {
-      width: 80%;
-      height: 300px;
-      margin: 0 auto;
-      padding: 20px;
-      border-radius: 10px;
-      background-color: #f5f5f5;
-      box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
-      line-height: 1.6;
-      white-space: pre-wrap;
-      overflow-y: auto;
-      font-family: Arial, Helvetica, sans-serif;
-      z-index: 2;
-    }
-  </style>
 </html>
diff --git a/online-editor.js b/online-editor.js
index 3e621d4..25853c7 100644
--- a/online-editor.js
+++ b/online-editor.js
@@ -2,9 +2,11 @@ const besUrl = 'http://localhost:225/api/v2/check'
 
 let besEditors = [] // Collection of all grammar checking services in the document
 
+// TODO: Add support for <textarea>
+
 class BesEditor {
   constructor(edit, CKEditorInstance) {
-    this.el = edit
+    this.editorElement = edit
     this.timer = null
     this.children = []
     const { correctionPanel, scrollPanel } = this.createCorrectionPanel(edit)
@@ -12,9 +14,9 @@ class BesEditor {
     this.scrollPanel = scrollPanel
     this.offsetTop = null
     this.CKEditorInstance = CKEditorInstance
-    if (!this.CKEditorInstance) edit.classList.add('bes-online-editor')
     this.originalSpellcheck = edit.spellcheck
     edit.spellcheck = false
+    this.abortController = new AbortController()
     this.proof(edit)
     edit.addEventListener('beforeinput', BesEditor.handleBeforeInput, false)
     edit.addEventListener('click', BesEditor.handleClick)
@@ -37,60 +39,42 @@ class BesEditor {
    * Unregisters grammar checking service
    */
   unregister() {
-    this.el.removeEventListener('scroll', BesEditor.handleScroll)
-    this.el.removeEventListener('click', BesEditor.handleClick)
-    this.el.removeEventListener(
+    this.editorElement.removeEventListener('scroll', BesEditor.handleScroll)
+    this.editorElement.removeEventListener('click', BesEditor.handleClick)
+    this.editorElement.removeEventListener(
       'beforeinput',
       BesEditor.handleBeforeInput,
       false
     )
     if (this.timer) clearTimeout(this.timer)
     besEditors = besEditors.filter(item => item !== this)
-    this.el.spellcheck = this.originalSpellcheck
-    this.el.classList.remove('bes-online-editor')
+    this.editorElement.spellcheck = this.originalSpellcheck
     this.correctionPanel.remove()
     this.scrollPanel.remove()
   }
 
-  // TODO: add support for textarea elements
   /**
    * Recursively grammar-proofs a DOM tree.
    *
-   * @param {Node} el DOM root node to proof
+   * @param {Node} node DOM root node to proof
    * @returns {Array} Markup of text to proof using BesStr
    */
-  async proof(el) {
-    // If first child is not a block element, add a dummy <div>...</div> around it.
-    // This solution is still not fully tested and might need some improvements.
-    if (el.classList?.contains('bes-online-editor')) {
-      const firstChild = el.firstChild
-      if (
-        firstChild &&
-        (firstChild.nodeType === Node.TEXT_NODE ||
-          !BesEditor.isBlockElement(firstChild))
-      ) {
-        const divEl = document.createElement('div')
-        if (firstChild.nodeType === Node.TEXT_NODE) {
-          divEl.textContent = firstChild.textContent
-        } else divEl.appendChild(firstChild.cloneNode(true))
-        el.insertBefore(divEl, firstChild)
-        el.removeChild(firstChild)
-      }
-    }
-
-    switch (el.nodeType) {
+  async proof(node) {
+    switch (node.nodeType) {
       case Node.TEXT_NODE:
-        return [{ text: el.textContent, el: el, markup: false }]
+        return [{ text: node.textContent, node: node, markup: false }]
 
       case Node.ELEMENT_NODE:
-        if (BesEditor.isBlockElement(el)) {
+        if (BesEditor.isBlockElement(node)) {
           // Block elements are grammar-proofed independently.
-          if (this.isProofed(el)) {
-            return [{ text: '<' + el.tagName + '/>', el: el, markup: true }]
+          if (this.isProofed(node)) {
+            return [
+              { text: '<' + node.tagName + '/>', node: node, markup: true }
+            ]
           }
-          this.clearMistakeMarkup(el)
+          this.clearMistakeMarkup(node)
           let data = []
-          for (const el2 of el.childNodes) {
+          for (const el2 of node.childNodes) {
             data = data.concat(await this.proof(el2))
           }
           if (data.some(x => !x.markup && !/^\s*$/.test(x.text))) {
@@ -101,7 +85,7 @@ class BesEditor {
                   x.markup ? { markup: x.text } : { text: x.text }
                 )
               }),
-              language: el.lang ? el.lang : 'sl',
+              language: node.lang ? node.lang : 'sl',
               level: 'picky'
             }
             const request = new Request(besUrl, {
@@ -109,7 +93,8 @@ class BesEditor {
               headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
               body: new URLSearchParams(requestData)
             })
-            fetch(request)
+            const signal = this.abortController.signal
+            fetch(request, { signal })
               .then(response => {
                 if (!response.ok) {
                   // TODO: Make connectivity and BesStr issues non-fatal. But show an error sign somewhere in the UI.
@@ -134,7 +119,7 @@ class BesEditor {
                         startingOffset + data[idx].text.length
                     ) {
                       range.setStart(
-                        data[idx].el,
+                        data[idx].node,
                         match.offset - startingOffset
                       )
                       break
@@ -153,7 +138,7 @@ class BesEditor {
                       /*startingOffset <= endOffset &&*/ endOffset <=
                         startingOffset + data[idx].text.length
                     ) {
-                      range.setEnd(data[idx].el, endOffset - startingOffset)
+                      range.setEnd(data[idx].node, endOffset - startingOffset)
                       break
                     }
                   }
@@ -167,37 +152,34 @@ class BesEditor {
                     match: match
                   })
                 })
-                this.markProofed(el, matches)
-
-                // This is a solution for displaying mistakes in CKEditor. It is not the best solution, but it works for now.
-                if (this.CKEditorInstance) {
-                  const resizeEvent = new Event('resize')
-                  window.dispatchEvent(resizeEvent)
-                }
+                this.markProofed(node, matches)
               })
               .catch(error => {
+                if (error.name === 'AbortError') return
                 // TODO: Make parsing issues non-fatal. But show an error sign somewhere in the UI.
                 throw new Error(
                   'Parsing backend server response failed: ' + error
                 )
               })
           }
-          return [{ text: '<' + el.tagName + '/>', el: el, markup: true }]
+          return [{ text: '<' + node.tagName + '/>', node: node, markup: true }]
         } else {
           // Surround inline element with dummy <tagName>...</tagName>.
-          let data = [{ text: '<' + el.tagName + '>', el: el, markup: true }]
-          for (const el2 of el.childNodes) {
+          let data = [
+            { text: '<' + node.tagName + '>', node: node, markup: true }
+          ]
+          for (const el2 of node.childNodes) {
             data = data.concat(await this.proof(el2))
           }
           data.splice(data.length, 0, {
-            text: '</' + el.tagName + '>',
+            text: '</' + node.tagName + '>',
             markup: true
           })
           return data
         }
 
       default:
-        return [{ text: '<?' + el.nodeType + '>', el: el, markup: true }]
+        return [{ text: '<?' + node.nodeType + '>', node: node, markup: true }]
     }
   }
 
@@ -226,9 +208,10 @@ class BesEditor {
    */
   static handleBeforeInput(event) {
     const edit = event.target
-    let editor = besEditors.find(e => e.el === edit)
+    let editor = besEditors.find(e => e.editorElement === edit)
     if (!editor) return
     if (editor.timer) clearTimeout(editor.timer)
+    editor.abortController.abort()
     let blockElements = new Set()
     event.getTargetRanges().forEach(range => {
       BesEditor.getNodesInRange(range).forEach(el =>
@@ -244,6 +227,7 @@ class BesEditor {
       editor.repositionMistakes()
     }, 0)
     editor.timer = setTimeout(function () {
+      editor.abortController = new AbortController()
       editor.proof(edit)
     }, 1000)
   }
@@ -255,7 +239,7 @@ class BesEditor {
    * @returns {Boolean} true if the element has already been grammar-proofed; false otherwise.
    */
   isProofed(el) {
-    return this.children.find(child => child.elements === el)?.isProofed
+    return this.children.find(child => child.element === el)?.isProofed
   }
 
   /**
@@ -268,9 +252,12 @@ class BesEditor {
     this.removeChild(el)
     this.children.push({
       isProofed: true,
-      elements: el, // TODO: Rename "elements" to "el" - 1. It contains only single element (plural elements is misleading), 2. BesEditor also uses "el" named field for DOM matching.
+      element: el,
       matches: matches
     })
+
+    // This is a solution for displaying mistakes in CKEditor. It is not the best solution, but it works for now.
+    if (this.CKEditorInstance) window.dispatchEvent(new Event('resize'))
   }
 
   /**
@@ -279,12 +266,14 @@ class BesEditor {
    * @param {Element} el DOM element that we should re-grammar-proof
    */
   clearMistakeMarkup(el) {
-    let child = this.children.find(child => child.elements === el)
+    let child = this.children.find(child => child.element === el)
     if (!child) return
     child.isProofed = false
     child.matches.forEach(match => {
-      match?.highlights.forEach(h => h.remove())
-      delete match.highlights
+      if (match?.highlights) {
+        match.highlights.forEach(h => h.remove())
+        delete match.highlights
+      }
     })
   }
 
@@ -294,7 +283,7 @@ class BesEditor {
    * @param {Element} el DOM element for removal
    */
   removeChild(el) {
-    this.children = this.children.filter(child => child.elements !== el)
+    this.children = this.children.filter(child => child.element !== el)
   }
 
   /**
@@ -302,7 +291,7 @@ class BesEditor {
    */
   repositionMistakes() {
     this.children.forEach(child => {
-      this.clearMistakeMarkup(child.elements)
+      this.clearMistakeMarkup(child.element)
       child.matches.forEach(match => {
         const { clientRects, highlights } = this.addMistakeMarkup(match.range)
         match.rects = clientRects
@@ -318,7 +307,6 @@ class BesEditor {
    * @returns {Object} Client rectangles and grammar mistake highlight elements
    */
   addMistakeMarkup(range) {
-    // TODO: Consider using range.getClientRects() instead of range.getBoundingClientRect()
     // In CKEditor case, the highlight element is not shown for some reason. But after resizing the window it is shown.
     const clientRects = range.getClientRects()
     const scrollPanelRect = this.scrollPanel.getBoundingClientRect()
@@ -343,7 +331,7 @@ class BesEditor {
    * Tests if given element is block element.
    *
    * @param {Element} el DOM element
-   * @returns false if CSS display property is inline or inline-block; true otherwise.
+   * @returns false if CSS display property is inline; true otherwise.
    */
   static isBlockElement(el) {
     switch (
@@ -353,7 +341,6 @@ class BesEditor {
         .toLowerCase()
     ) {
       case 'inline':
-      case 'inline-block':
         return false
       default:
         return true
@@ -367,7 +354,7 @@ class BesEditor {
    * @returns {Element} Innermost block element containing given node
    */
   getBlockParent(el) {
-    for (; el && el !== this.el; el = el.parentNode) {
+    for (; el && el !== this.editorElement; el = el.parentNode) {
       if (el.nodeType === Node.ELEMENT_NODE && BesEditor.isBlockElement(el))
         return el
     }
@@ -454,7 +441,7 @@ class BesEditor {
    */
   static handleClick(event) {
     const edit = BesEditor.findParent(event.target)
-    let editor = besEditors.find(e => e.el === edit)
+    let editor = besEditors.find(e => e.editorElement === edit)
     if (!editor) return
     const target = editor.getBlockParent(event.target)
     editor.renderPopup(target, event.clientX, event.clientY)
@@ -469,13 +456,13 @@ class BesEditor {
    */
   static handleScroll(event) {
     const edit = event.target
-    let editor = besEditors.find(e => e.el === edit)
+    let editor = besEditors.find(e => e.editorElement === edit)
     if (!editor) return
     editor.scrollPanel.style.top = -edit.scrollTop + 'px'
     editor.offsetTop = edit.scrollTop
     setTimeout(() => {
       editor.repositionMistakes()
-    }, 300)
+    }, 100)
     // TODO: Move popup (if open) too.
   }
 
@@ -487,10 +474,7 @@ class BesEditor {
    */
   static findParent(el) {
     for (; el; el = el.parentNode) {
-      if (
-        el.classList?.contains('bes-online-editor') ||
-        el.classList?.contains('ck-editor__editable') // Find a better way to handle CKEditor
-      ) {
+      if (besEditors.find(editor => editor.editorElement === el)) {
         return el
       }
     }
@@ -506,7 +490,7 @@ class BesEditor {
    */
   renderPopup(el, clientX, clientY) {
     const popup = document.querySelector('bes-popup-el')
-    const matches = this.children.find(child => child.elements === el)?.matches
+    const matches = this.children.find(child => child.element === el)?.matches
     if (matches) {
       for (let m of matches) {
         if (m.rects) {
@@ -516,8 +500,7 @@ class BesEditor {
               m.match.replacements.forEach(replacement => {
                 popup.appendReplacements(
                   el,
-                  r,
-                  m.match,
+                  m,
                   replacement.value,
                   this
                 )
@@ -534,17 +517,15 @@ class BesEditor {
 
   // TODO: In rich HTML texts, match.offset has different value than in plain text.
   // This function should be able to handle both cases or find a way that works for both.
-  static replaceText(el, rect, match, replacement, editor) {
+  replaceText(el, match, replacement) {
+    if (this.timer) clearTimeout(this.timer)
+    this.abortController.abort()
     // const tags = this.getTagsAndText(el)
-    if (!editor.CKEditorInstance) {
-      const text = el.textContent
-      const newText =
-        text.substring(0, match.offset) +
-        replacement +
-        text.substring(match.offset + match.length)
-      el.textContent = newText
+    if (!this.CKEditorInstance) {
+      match.range.deleteContents()
+      match.range.insertNode(document.createTextNode(replacement))
     } else {
-      const { CKEditorInstance } = editor
+      const { CKEditorInstance } = this
       CKEditorInstance.model.change(writer => {
         const viewElement =
           CKEditorInstance.editing.view.domConverter.mapDomToView(el)
@@ -552,15 +533,15 @@ class BesEditor {
           CKEditorInstance.editing.mapper.toModelElement(viewElement)
         if (modelElement) {
           const elementRange = writer.createRangeIn(modelElement)
-          // TODO: This logic should work once the HTML tags are removed from match.offset and match.length if is possible.
+          // TODO: This logic should work once the HTML tags are removed from match.match.offset and match.match.length if is possible.
           if (
-            elementRange.start.offset <= match.offset &&
-            elementRange.end.offset >= match.offset + match.length
+            elementRange.start.offset <= match.match.offset &&
+            elementRange.end.offset >= match.match.offset + match.match.length
           ) {
-            const start = writer.createPositionAt(modelElement, match.offset)
+            const start = writer.createPositionAt(modelElement, match.match.offset)
             const end = writer.createPositionAt(
               modelElement,
-              match.offset + match.length
+              match.match.offset + match.match.length
             )
             const range = writer.createRange(start, end)
             writer.remove(range)
@@ -569,11 +550,12 @@ class BesEditor {
         }
       })
     }
-    BesEditor.clearSingleMistake(editor, el, rect)
+    this.clearMistakeMarkup(el)
     // In my opinion, this approach provides the most straightforward solution for repositioning mistakes after a change.
     // It maintains reasonable performance as it only checks the block element that has been modified,
     // rather than re-evaluating the entire document or a larger set of elements.
-    editor.proof(el)
+    this.abortController = new AbortController()
+    this.proof(el)
   }
 
   // static getTagsAndText(node) {
@@ -590,25 +572,6 @@ class BesEditor {
   //   }
   // }
 
-  // This function clears a single mistake
-  static clearSingleMistake(editor, el, rect) {
-    const childToDelete = editor.children.filter(
-      child => child.elements === el
-    )[0]
-    childToDelete.isProofed = false
-    childToDelete.matches = childToDelete.matches.filter(
-      match => !BesEditor.isPointInRect(rect.left, rect.top, match.rects[0])
-    )
-
-    // TODO: find a better way to remove elements from the DOM
-    Array.from(editor.scrollPanel.children)
-      .filter(child => {
-        const childRect = child.getBoundingClientRect()
-        return BesEditor.isPointInRect(childRect.left, childRect.top, rect)
-      })
-      .forEach(child => child.remove())
-  }
-
   setCorrectionPanelSize(editor, correctionPanel, scrollPanel) {
     const styles = window.getComputedStyle(editor)
     const totalWidth =
@@ -648,12 +611,12 @@ window.onload = () => {
 window.onresize = () => {
   besEditors.forEach(editor => {
     editor.setCorrectionPanelSize(
-      editor.el,
+      editor.editorElement,
       editor.correctionPanel,
       editor.scrollPanel
     )
     editor.children.forEach(child => {
-      editor.clearMistakeMarkup(child.elements)
+      editor.clearMistakeMarkup(child.element)
       child.matches.forEach(match => {
         const { clientRects, highlights } = editor.addMistakeMarkup(match.range)
         match.rects = clientRects
@@ -775,14 +738,14 @@ class BesPopupEl extends HTMLElement {
     this.shadowRoot.querySelector('.popup-text').textContent = text
   }
 
-  appendReplacements(el, rect, match, replacement, editor) {
+  appendReplacements(el, match, replacement, editor) {
     const replacementDiv = this.shadowRoot.querySelector('.bes-replacement-div')
     const replacementBtn = document.createElement('button')
     replacementBtn.classList.add('bes-replacement-btn')
     replacementBtn.textContent = replacement
     replacementBtn.classList.add('bes-replacement')
     replacementBtn.addEventListener('click', () => {
-      BesEditor.replaceText(el, rect, match, replacement, editor)
+      editor.replaceText(el, match, replacement)
     })
     replacementDiv.appendChild(replacementBtn)
   }