diff --git a/docs/topics/reading-and-writing-to-file.md b/docs/topics/reading-and-writing-to-file.md
index abd7c5f3..13b62e01 100644
--- a/docs/topics/reading-and-writing-to-file.md
+++ b/docs/topics/reading-and-writing-to-file.md
@@ -703,43 +703,24 @@ echo $writer->generateSheetData();
 echo $writer->generateHTMLFooter();
 ```
 
-#### Editing HTML During Save Via a Callback
+#### Editing HTML during save via a callback
 
 You can also add a callback function to edit the generated html
-before saving. For example, you could add a webfont
-(not currently supported for Pdf) as follows:
+before saving. For example, you could change the gridlines
+from a thin solid black line:
 
 ``` php
-function webfont(string $html): string
+function changeGridlines(string $html): string
 {
-    $linktag = <<<EOF
-<link href="https://fonts.googleapis.com/css2?family=Poiret+One&display=swap" rel="stylesheet" />
-
-EOF;
-    $html = preg_replace('@<style@', "$linktag<style", $html, 1);
-    $html = str_replace("font-family:'Calibri';",
-        "font-family:'Poiret One','Calibri',sans-serif;",
+    return str_replace('{border: 1px solid black;}',
+        '{border: 2px dashed red;}',
         $html);
-
-    return $html;
 }
 $writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet);
-$writer->setEditHtmlCallback('webfont');
+$writer->setEditHtmlCallback('changeGridlines');
 $writer->save($filename);
 ```
 
-#### Writing UTF-8 HTML files
-
-A HTML file can be marked as UTF-8 by writing a BOM file header. This
-can be enabled by using the following code:
-
-``` php
-$writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet);
-$writer->setUseBOM(true);
-
-$writer->save("05featuredemo.htm");
-```
-
 #### Decimal and thousands separators
 
 See section `\PhpOffice\PhpSpreadsheet\Writer\Csv` how to control the
@@ -866,7 +847,7 @@ $writer->setPreCalculateFormulas(false);
 $writer->save("05featuredemo.pdf");
 ```
 
-#### Editing Pdf During Save Via a Callback
+#### Editing Pdf during save via a callback
 
 You can also add a callback function to edit the html used to
 generate the Pdf before saving.
diff --git a/samples/Basic/17b_Html.php b/samples/Basic/17b_Html.php
index 05649314..97bb29a3 100644
--- a/samples/Basic/17b_Html.php
+++ b/samples/Basic/17b_Html.php
@@ -8,20 +8,13 @@ $spreadsheet = require __DIR__ . '/../templates/sampleSpreadsheet.php';
 $filename = $helper->getFilename(__FILE__, 'html');
 $writer = new Html($spreadsheet);
 
-function webfont(string $html): string
+function changeGridlines(string $html): string
 {
-    $linktag = <<<EOF
-<link href="https://fonts.googleapis.com/css2?family=Poiret+One&display=swap" rel="stylesheet" />
-
-EOF;
-    $html = preg_replace('@<style@', "$linktag<style", $html, 1);
-    $html = str_replace("font-family:'Calibri';", "font-family:'Poiret One','Calibri',sans-serif;", $html);
-
-    return $html;
+    return str_replace('{border: 1px solid black;}', '{border: 2px dashed red;}', $html);
 }
 
 $callStartTime = microtime(true);
 $writer->setEmbedImages(true);
-$writer->setEditHtmlCallback('webfont');
+$writer->setEditHtmlCallback('changeGridlines');
 $writer->save($filename);
 $helper->logWrite($writer, $filename, $callStartTime);
diff --git a/samples/Pdf/21a_Pdf.php b/samples/Pdf/21a_Pdf.php
index c4dc2c48..b5572afe 100644
--- a/samples/Pdf/21a_Pdf.php
+++ b/samples/Pdf/21a_Pdf.php
@@ -1,9 +1,7 @@
 <?php
 
 use PhpOffice\PhpSpreadsheet\Worksheet\PageSetup;
-use PhpOffice\PhpSpreadsheet\Writer\Pdf\Dompdf;
 use PhpOffice\PhpSpreadsheet\Writer\Pdf\Mpdf;
-use PhpOffice\PhpSpreadsheet\Writer\Pdf\Tcpdf;
 
 require __DIR__ . '/../Header.php';
 $spreadsheet = require __DIR__ . '/../templates/sampleSpreadsheet.php';
@@ -13,35 +11,15 @@ $spreadsheet->getActiveSheet()->setShowGridLines(false);
 
 $helper->log('Set orientation to landscape');
 $spreadsheet->getActiveSheet()->getPageSetup()->setOrientation(PageSetup::ORIENTATION_LANDSCAPE);
+$spreadsheet->setActiveSheetIndex(0)->setPrintGridlines(true);
 
-function yellowBody(string $html): string
+function changeGridlines(string $html): string
 {
-    $newstyle = <<<EOF
-<style type='text/css'>
-body {
-background-color: yellow;
+    return str_replace('{border: 1px solid black;}', '{border: 2px dashed red;}', $html);
 }
-</style>
-
-EOF;
-
-    return preg_replace('@</head>@', "$newstyle</head>", $html);
-}
-
-$helper->log('Write to Dompdf');
-$writer = new Dompdf($spreadsheet);
-$filename = $helper->getFileName('21a_Pdf_dompdf.xlsx', 'pdf');
-$writer->setEditHtmlCallback('yellowBody');
-$writer->save($filename);
 
 $helper->log('Write to Mpdf');
 $writer = new Mpdf($spreadsheet);
 $filename = $helper->getFileName('21a_Pdf_mpdf.xlsx', 'pdf');
-$writer->setEditHtmlCallback('yellowBody');
-$writer->save($filename);
-
-$helper->log('Write to Tcpdf');
-$writer = new Tcpdf($spreadsheet);
-$filename = $helper->getFileName('21a_Pdf_tcpdf.xlsx', 'pdf');
-$writer->setEditHtmlCallback('yellowBody');
+$writer->setEditHtmlCallback('changeGridlines');
 $writer->save($filename);
diff --git a/src/PhpSpreadsheet/Writer/Html.php b/src/PhpSpreadsheet/Writer/Html.php
index 963b02d7..752f286f 100644
--- a/src/PhpSpreadsheet/Writer/Html.php
+++ b/src/PhpSpreadsheet/Writer/Html.php
@@ -134,9 +134,9 @@ class Html extends BaseWriter
     /**
      * Callback for editing generated html.
      *
-     * @var callable
+     * @var null|callable
      */
-    protected $editHtmlCallback = '';
+    protected $editHtmlCallback;
 
     /**
      * Create a new HTML.
@@ -197,9 +197,9 @@ class Html extends BaseWriter
 
         // Write footer
         $html .= $this->generateHTMLFooter();
-        $cbk = $this->editHtmlCallback;
-        if ($cbk) {
-            $html = $cbk($html);
+        $callback = $this->editHtmlCallback;
+        if ($callback) {
+            $html = $callback($html);
         }
 
         Calculation::setArrayReturnType($saveArrayReturnType);
@@ -208,16 +208,11 @@ class Html extends BaseWriter
         return $html;
     }
 
-    public function setEditHtmlCallback(callable $cbk): void
+    public function setEditHtmlCallback(?callable $cbk): void
     {
         $this->editHtmlCallback = $cbk;
     }
 
-    public function resetEditHtmlCallback(): void
-    {
-        $this->editHtmlCallback = '';
-    }
-
     const VALIGN_ARR = [
         Alignment::VERTICAL_BOTTOM => 'bottom',
         Alignment::VERTICAL_TOP => 'top',
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php b/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php
index f712419c..388dbd0e 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php
@@ -33,7 +33,7 @@ EOF;
         $html1 = $writer->generateHTMLall();
         $writer->setEditHtmlCallback([$this, 'yellowBody']);
         $html2 = $writer->generateHTMLall();
-        $writer->resetEditHtmlCallback();
+        $writer->setEditHtmlCallback(null);
         $html3 = $writer->generateHTMLall();
 
         self::assertFalse(strpos($html1, 'background-color: yellow'));