Is it a bad practice to use custom HTML attributes and style them with CSS?

Question

Is there any problem creating a CSS class like this:

[test] { font: 13px; }

and use it in an HTML attribute as this:

&

Answer 1

HTML:


CSS:
.test { font:13px; }

its good to use classes. Example:

/* All these match that */
.module { }
.accordion { }
.expand { }