what is this type of CSS code? [duplicate]

Question

this is a html code in a webpage:

<div class="3u">

...

</div>

It styled with css in this way:

.\33 u, .\33 u\24, .\33 u\28 1\29, .\33 u\24\28 1\29 { width: 25%; clear: none; }

Can anybody explain me what is this?

I familar with CSS but Not this type!

Answer 1

You technically can't start a CSS selector with a number. However, you can use escape characters to get around that it looks like. Check this out.

Leading digits

If the first character of an identifier is numeric, you’ll need to escape it based on its Unicode code point. For example, the code point for the character 1 is U+0031, so you would escape it as \000031 or \31 .

Basically, to escape any numeric character, just prefix it with \3 and append a space character ( ). Yay Unicode!