function initPage() {
var inputs = document.getElementsByTagName("input");
for (var i=0; i<inputs.length; i++) {
if (inputs[i].className.indexOf("bt-") != -1 ) {
inputs[i].onmouseover = function()
{
this.src = this.src.replace(".gif", "-hover.gif");
}
inputs[i].onmouseout = function()
{
this.src = this.src.replace("-hover.gif", ".gif");
}
}
}
}

if (window.addEventListener)
window.addEventListener("load", initPage, false);
else if (window.attachEvent)
window.attachEvent("onload", initPage);