[tbworld]

Revised: Had no idea this was part of a mod, when I commented. So what I was explaining is totally out of context and probably worthless. Sorry.

"Mouseover" is a JavaScript "Event". "Pseudo selector class "hover" is CSS. Not sure which one you are talking about, but I am guessing "hover". You cannot embed a "selector pseudo class" directly in the HTML it must be contained within a style element. For vbulletin add this class to "additional.css" if you are a beginner.

You want do something like this:

<style>
    .divstyle {
         height: 15px;
         width: 15px;
         background: #FF0000;
    }
    .divstyle:hover {
        color:red;   /* whatever color you want for foreground text */
    }
</style>

<div class="divstyle"></div>

The css in the style tags should really be inserted into additional.css.
See CSS Pseudo Selectors for more information.