The site I'm working on is here > http://www.activeinternational.com/MEXOP/

To recreate the problem, click on the blue box that has arrow pointing to the right. That will open a lightbox video player. At the bottom right hand corner of the player window you should see a the text "Cerrar".

It shows fine in Chrome, Firefox and Safari. However, on IE, its a no show. What gives?

Here's the css I'm using (many of the rules are just for tracing the layout in IE to confirm the anchor element is present.)

Code:
a#mbCloseLink{
background:none !important;
border:1px solid #fff !important;
display:block !important;
height:20px;
width:100px;
zoom:1
}

a#mbCloseLink:before{
content:'Cerrar';
height:20px;
width:100px;
}