This is only viewable in Internet Explorer. This script will make an image grey until it has a mouse over it. Once you mouseoff, it changes back to grey. Copy and paste this code into your <img>command.
style="filter:progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)" onmouseover="this.style.filter = 'progid:DXImageTransform.Microsoft.BasicImage(grayscale=0)'" onmouseout="this.style.filter = 'progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)'"
To see the effect move your mouse to the following image.
More HTML and CSS: 
