you have to do it with javascript or css. you can't have it just plain html and have a rollover... however you can have it set with just a background or an image that is the same color as the background for the inactive state and an image for the mouseover. unless you're using css for the layout I'd recommend using a simple javascript.
<script language="JavaScript">
<!--
function MM_findObj(n, d) { //v4.01
var p,i,x; if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[n];
for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers.document);
if(!x && d.getElementById) x=d.getElementById(n); return x;
}
function MM_swapImage() { //v3.0
var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
if ((x=MM_findObj(a))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}
function MM_swapImgRestore() { //v3.0
var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a)&&x.oSrc;i++) x.src=x.oSrc;
}
function MM_preloadImages() { //v3.0
var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)
if (a.indexOf("#")!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a;}}
}
//-->
</script>
</head>
<body bgcolor="#ffffff" onLoad="MM_preloadImages('image name +extension (eg. .gif or .jpg');">
<td><img name="rollover image name or background" src="image name" >
</td>
<td><a href="#" onMouseOut="MM_swapImgRestore();" onMouseOver="MM_swapImage('image name','','image name +extension',1);"><img name="image name" src="image name + extension"></a></td>