Browser Compatibility [help]

Hello, i am quite new to WordPress.

I have coded these main welcome buttons on this site as simple rollover buttons specified within the CSS. But for some reason they do not show when in IE or Firefox?

https://www.eurathlon.eu/site/

a:hover.testrollover {
	background-position: -200px 0;
}

.testrollover a
{
display: block;
width: 200px;
height: 200px;
background: url('https://www.eurathlon.eu/site/wp-content/uploads/2014/09/button11.jpg') no-repeat;
text-decoration: none;
float: left;
text-indent:-5000px;

}

Could some one please point out why this isn’t working?

Thanks