Apparently spurious errors in the Nu Html Checker

I used the Nu Html Checker <https://validator.w3.org/nu/> (version 
23.1.17) on a webpage of mine and found several errors, but I also had 
five errors that appear to be spurious.

Specifically, the two CSS declarations generate errors because the 
checker mysteriously inserts the letters “fon” (or sometimes 
“fo”) in the middle of the declaration, turning “{ font-family” 
into “{ fon font-family”. I tried two slightly different versions of 
the same declaration with the same results. Clicking on the line/column 
number highlights specifically the letter ’n’ in the spurious word 
‘fon’.

In four places, the checker generates a warning that “Text run is not 
in Unicode Normalization Form C” even though I ran the relevant text 
through the Perl function Unicode::Normalize NFC() and got byte-for-byte 
the same exact strings back. Three of the strings are in the N’Ko 
language and character set (a fairly recent addition to the Unicode 
standard); the fourth is in the Kashmiri language in the Perso-Arabic 
character set. They are in the following locations:
1. +229 Benin, lang=nqo
2. +57 Colombia, lang=nqo
3. +672 Au Ext Terr, lang=ks-Arab, and
4. +967 Yemen, lang=nqo
I placed comments marked ###HERE### at each location for ease of 
reference. Note that I was not able to find the N’Ko translation for 
“Australian External Territories.”

Thank you for an extremely useful tool; I hope that this error report 
can help make it even better.

Here are the errors and warnings reported:

Error: CSS: Parse Error. At line 14, column 64
Error: CSS: Parse Error. At line 14, column 64 (duplicate error for no 
apparent reason)
Error: CSS: Parse Error. At line 18, column 56

Warning: Text run is not in Unicode Normalization Form C.
 From line 52, column 49, to line 52, column 53
 From line 78, column 44, to line 78, column 52
 From line 103, column 48, to line 103, column 66
 From line 141, column 51, to line 141, column 55

Here is the stripped-down HTML/CSS of that page:

- = - = - = - = - = - = - = - = - = - = - = - = -

<code>
<!DOCTYPE html>
<html lang="en" dir="rtl">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title dir="rtl">☎️🔢🌏🌍🌎🔡🖥</title>

 <script>
  let visibleScrollbars = window.scrollbars.visible;
 </script>
 

<style>
 :where(:lang(ff), :lang(fuc), :lang(fuf), :lang(*-Adlm)) {
  font-family: 'Noto Sans Adlam', sans-serif;
 }
 
 :lang(ff), :lang(fuc), :lang(fuf), :lang(*-Adlm) {
  font-family: 'Noto Sans Adlam', sans-serif;
 }

</style>
</head>
<body dir="rtl">

<main dir="rtl">
<table id="main-table" dir="rtl">
<tbody>

<tr><!-- +229 Benin -->
 <th class="col-cc" dir="ltr" scope="row">+229</th>
 <th class="col-iso" translate="no" dir="ltr" scope="row">BJ</th>
 <th class="col-flag" scope="row">🇧🇯</th>
 <td class="col-name" lang="ar" dir="rtl">
  <span lang="ar">بنين</span>
  <span class="fs78" lang="arz">(بينين)</span>
 </td>
 <td class="col-name" lang="ckb" dir="rtl">بێنین</td>
 <td class="col-name" lang="fa" dir="rtl">بنين</td>
 <td class="col-name" lang="mzn" dir="rtl">بنین</td>
 <td class="col-name" lang="azb" dir="rtl">بنین</td>
 <td class="col-name" lang="ps" dir="rtl">بینین</td>
 <td class="col-name" lang="ur" dir="rtl">بینن</td>
 <td class="col-name" lang="sd" dir="rtl">بينن</td>
 <td class="col-name" lang="pnb" dir="rtl">بنين</td>
 <td class="col-name" lang="ks-Arab" dir="rtl">بِنِن</td>
 <td class="col-name" lang="kk-Arab" dir="rtl">بەنىين</td>
 <td class="col-name" lang="ug" dir="rtl">بېنىن</td>
 <td class="col-name" lang="he" dir="rtl">בֶּנִין</td>
 <td class="col-name" lang="yi" dir="rtl">בענין</td>
 <td class="col-name" lang="syr" dir="rtl">ܒܢܝܢ</td>
 <td class="col-name" lang="nqo" dir="rtl">ߓߣߍ߲߫</td><!-- 
###HERE### -->
 <td class="col-name" lang="ff-Adlm" dir="rtl">𞤄𞤫𞤲𞤫𞤲</td>
 <td class="col-name" lang="dv" dir="rtl">ބެނީން</td>
 <td class="col-name" lang="en" dir="ltr"><span 
lang="fr">Bénin</span></td>
 <td class="col-misc" dir="rtl">&nbsp;</td>
</tr><!-- +229 Benin -->

<tr><!-- +57 Colombia -->
 <th class="col-cc" dir="ltr" scope="row">+57</th>
 <th class="col-iso" translate="no" dir="ltr" scope="row">CO</th>
 <th class="col-flag" scope="row">🇨🇴</th>
 <td class="col-name" lang="ar" dir="rtl"><span 
lang="ar">كولومبيا</span></td>
 <td class="col-name" lang="ckb" dir="rtl">کۆلۆمبیا</td>
 <td class="col-name" lang="fa" dir="rtl">کلمبیا</td>
 <td class="col-name" lang="mzn" dir="rtl">کلمبیا</td>
 <td class="col-name" lang="azb" dir="rtl">کولومبیا</td>
 <td class="col-name" lang="ps" dir="rtl">کولمبیا</td>
 <td class="col-name" lang="ur" dir="rtl">كولومبيا</td>
 <td class="col-name" lang="sd" dir="rtl">ڪولمبيا</td>
 <td class="col-name" lang="pnb" dir="rtl">کولمبیا</td>
 <td class="col-name" lang="ks-Arab" dir="rtl">کولومبیٛا</td>
 <td class="col-name" lang="kk-Arab" dir="rtl">كولۋمبىييا</td>
 <td class="col-name" lang="ug" dir="rtl">كولومبىيە</td>
 <td class="col-name" lang="he" 
dir="rtl">קוֹלוֹמְבְּיָה</td>
 <td class="col-name" lang="yi" dir="rtl">קאָלאָמביע</td>
 <td class="col-name" lang="syr" dir="rtl">ܩܘܠܘܡܒܝܐ</td>
 <td class="col-name" lang="nqo" dir="rtl">ߞߏߟߏ߲߱ߓߌߊ</td><!-- 
###HERE### -->
 <td class="col-name" lang="ff-Adlm" 
dir="rtl">𞤑𞤮𞥊𞤤𞤮𞥊𞥅𞤥𞤦𞤭𞤴𞤢𞥄</td>
 <td class="col-name" lang="dv" dir="rtl">ކޮލަންބިއާ</td>
 <td class="col-name" lang="en" dir="ltr"><span lang="es" 
translate="yes">
  Colombia</span></td>
 <td class="fs78" dir="rtl">
  <span lang="qu" dir="ltr">Kulumbya</span> •
  <span lang="ay" dir="ltr">Kuluwya</span> •
  <span lang="gcr" dir="ltr">Lakolonbi</span>
 </td>
</tr><!-- +57 Colombia -->

<tr><!-- +672 Au Ext Terr -->
 <th class="col-cc" dir="ltr" scope="row">+672</th>
 <th class="col-iso" translate="no" dir="ltr" scope="row">&nbsp;</th>
 <th class="col-flag" scope="row">🇦🇺</th>
 <td class="col-name" lang="ar" dir="rtl"><span 
lang="ar">الأقاليم الخارجية 
الاسترالي</span></td>
 <td class="col-name" lang="ckb" dir="rtl">خاکەکانی 
دەرەوەی ئوسترالیا</td>
 <td class="col-name" lang="fa" dir="rtl">سرزمین های خارجی 
استرالیا</td>
 <td class="col-name" lang="mzn" dir="rtl">&nbsp;</td>
 <td class="col-name" lang="azb" dir="rtl">اوسترالییانئن 
خاریچی ەرازیلەری</td>
 <td class="col-name" lang="ps" dir="rtl">د استرالیا بهرنۍ 
سیمې</td>
 <td class="col-name" lang="ur" dir="rtl">آسٹریلیا کے 
بیرونی علاقے</td>
 <td class="col-name" lang="sd" dir="rtl">آسٽريليا جي 
ٻاهرين علائقن</td>
 <td class="col-name" lang="pnb" dir="rtl">آستریلیائی 
باہری پردیش</td>
 <td class="col-name" lang="ks-Arab" dir="rtl">آسٽريلين ڇ 
ٽريرٽري</td><!-- ###HERE### -->
 <td class="col-name" lang="kk-Arab" dir="rtl">اۆسترالىييا 
ىشكى اۋماعى</td>
 <td class="col-name" lang="ug" dir="rtl">ئاۋىستىرالىيە 
تاشقى رايونلىرى</td>
 <td class="col-name" lang="he" dir="rtl">טריטוריות 
חיצוניות של אוסטרליה</td>
 <td class="col-name" lang="yi" dir="rtl">אויסטראַליע 
פונדרויסנדיק טעריטאָריע</td>
 <td class="col-name" lang="syr" 
dir="rtl">ܡܕ݂ܰܪ̈ܟ݂ܘܳܬ݂ܪܳܐ ܕ݂ܩܽܘܝܳܡܳܐ</td>
 <td class="col-name" lang="fr" dir="ltr">Territoires extérieurs de 
l’Australie</td>
 <td class="col-name" lang="ff-Adlm" 
dir="rtl">𞤑𞤫𞥅𞤪𞤮𞥅𞤪𞤵𞤴𞤫 
𞤌𞤧𞤼𞤫𞤪𞤤𞤭𞥅𞤳𞤫 
𞤚𞤵𞤥𞤢𞤪𞤢𞤲𞤳𞤫</td>
 <td class="col-name" lang="dv" dir="rtl">އޮސްޓްރޭލިއާގެ 
ބޭރު ސަރަހައްދުތަކެވެ</td>
 <td class="col-name" lang="en" dir="ltr">Australian External 
Territories</td>
 <td class="col-misc" dir="rtl">&nbsp;</td>
</tr><!-- +672 Au Ext Terr -->

<tr><!-- +967 Yemen -->
 <th class="col-cc" dir="ltr" scope="row">+967</th>
 <th class="col-iso" translate="no" dir="ltr" scope="row">
  YE<br><span class="notyet" lang="ar" dir="rtl">
  &nbsp;(اليمن)&nbsp;</span>
 </th>
 <th class="col-flag" scope="row">🇾🇪</th>
 <td class="col-name" lang="ar" dir="rtl">
  <span lang="ar">ٱلْيَمَن</span>
  <span class="fs78" lang="ary">(ليامان)</span>
 </td>
 <td class="col-name" lang="ckb" dir="rtl">یەمەن</td>
 <td class="col-name" lang="fa" dir="rtl">یمن</td>
 <td class="col-name" lang="mzn" dir="rtl">یَمَن</td>
 <td class="col-name" lang="azb" dir="rtl">یمن</td>
 <td class="col-name" lang="ps" dir="rtl">يمن</td>
 <td class="col-name" lang="ur" dir="rtl">یمن</td>
 <td class="col-name" lang="sd" dir="rtl">يمن</td>
 <td class="col-name" lang="pnb" dir="rtl">یمن</td>
 <td class="col-name" lang="ks-Arab" dir="rtl">یَمَن</td>
 <td class="col-name" lang="kk-Arab" dir="rtl">يەمەن</td>
 <td class="col-name" lang="ug" dir="rtl">يەمەن</td>
 <td class="col-name" lang="he" dir="rtl">תימן</td>
 <td class="col-name" lang="yi" dir="rtl">תֵּימָן 
(יעמען)</td>
 <td class="col-name" lang="syr" dir="rtl">ܝܡܢ</td>
 <td class="col-name" lang="nqo" dir="rtl">ߦߡߊߣߌ߲߫</td><!-- 
###HERE### -->
 <td class="col-name" lang="ff-Adlm" dir="rtl">𞤒𞤢𞤥𞤢𞤲</td>
 <td class="col-name" lang="dv" dir="rtl">ޔަމަން</td>
 <td class="col-name" lang="en" dir="ltr">Yemen</td>
 <td class="col-misc" dir="rtl">&nbsp;</td>
</tr><!-- +967 Yemen -->

</tbody>
</table>
</main>

</body>
</html>
</code>

Received on Monday, 23 January 2023 08:59:57 UTC