var menuImgs=new Array();
function preload_img(id,src_a){
	var el=document.getElementById(id);
	if(!el||el.tagName!='IMG'){
		return;
	}
	menuImgs[id]=new Array(new Image(),new Image());
	menuImgs[id][0].src=src_a;
    menuImgs[id][1].src=el.src;
}
preload_img('m1','images/m1_a.gif');
preload_img('m2','images/m2_a.gif');
preload_img('m3','images/m3_a.gif');
preload_img('m4','images/m4_a.gif');
preload_img('m5','images/m5_a.gif');
preload_img('m6','images/m6_a.gif');
preload_img('m7','images/m7_a.gif');
function hover(obj){
	var id=obj.id;
	if(!menuImgs[id])
		return;
	obj.src=menuImgs[id][0].src;
}
function unhover(obj){
	var id=obj.id;
	if(!menuImgs[id])
		return;
	obj.src=menuImgs[id][1].src;
}