Escaping CSS digits, 0 is removed from CSS aggregated files The following HTML markup won't work on a production site.
&lt;div class=&quot;iconleft 109&quot;&gt;TEXT&lt;/div&gt;

This is the code in the custom.css file.
.iconleft.\31 09,
.iconleft.\31 12,
.iconleft.\31 10,
.iconleft.\31 11,
.iconleft.\31 20 {
  background: #B0CD00;
}

.iconleft.\31 09 works on localhost with xampp and no aggregation. On the production site, where Advanced CSS/JS Aggregation is activated, it wont work for 109.
In the aggregated CSS file, I see .iconleft.\31 9 as CSS class. It seems that 0 has been removed.
Do you have any hint?
I think the code is valid.
Anyway due to lack of time i decided to ad an &quot;id&quot; to the class. So the html is now
&lt;div class=&quot;iconleft id-{{ child_id }}&quot;&gt;Text&lt;/div&gt;

And the css
.iconleft.id-109,
.iconleft.id-112,
.iconleft.id-110,
.iconleft.id-111,
.iconleft.id-120 {
  background: #B0CD00;
}

This is working for me.
But if somebody knows why aggregation removes the &quot;0&quot; please let me know.