| Сообщение от Magneto   | 
	| var arayLink = document.getElementsByTagName('a'), | 
	

 ай-ай-ай
var a = /jpg$/,
    b, // current a
    c = 0,
    ie = !document.documentElement.addEventListener,
    handler = function(e){
        
        if (a.test( (event ? event.srcElement:e.target).href)) {
            alert("содержит");
        } else {
            alert("нет");
        }
    }
while ( b = document.links[c++] ) 
    ie ? b.attachEvent("onmouseover", handler ):b.addEventListener("mouseover",handler,false);
пример :
<a href="/mk" style="color:red">no jpg</a>
<a href="/lol.jpg" style="color:green">jpg</a>
<script>
var a = /jpg$/,
    b, // current a
    c = 0,
    ie = !document.documentElement.addEventListener,
    handler = function(e){
        
        if (a.test( (event ? event.srcElement:e.target).href)) {
            alert("содержит");
        } else {
            alert("нет");
        }
    }
while ( b = document.links[c++] ) 
    ie ? b.attachEvent("onmouseover", handler ):b.addEventListener("mouseover",handler,false);
</script>