Hi guys am trying to get my site validated and have got the following errors. Any ideas how I can rectify this

The default scripting language must be specified for an intrinsic event:
<div class="details" onmouseover="this.className='details2'"

I think it has something to do with the content type in my header which I have the following
<meta http-equiv="Content-Type" content="<?php bloginfo('html_type'); ?>; charset=<?php bloginfo('charset'); ?>" />

Any ideas guys???