img01    =new Image()
img01.src="images/arr1.gif"
img02    =new Image()
img02.src="images/arr.gif"
function imgover(imgname)
{
imgname.src=img01.src
}
function imgout(imgname)
{
imgname.src=img02.src
}
<!--
var f=0;
if(navigator.appVersion.substring(0,1)>=3) {f=1;};
if (f){ var imgB=new Image(); imgB.src="images/but/11a.gif"; var imgBB=new Image(); imgBB.src="images/but/11c.gif"; }
//-->