underline in js

Does anybody know, how to make underline when mouse is over??
I made something like that, but it hasn't worked...

<SCRIPT>
<!--
ie4 = ((navigator.appName == "Microsoft Internet Explorer") && (parseInt(navigator.appVersion) >= 4 ));
function over()
{ if (ie4) {
event.srcElement.style.cursor="hand";
event.srcElement.textDecoration="underline"; } } // there I don't know...
function out(){
if (ie4)
{ event.srcElement.style.cursor = "auto";
event.srcElement.textDecoration="none"; // there too...
} }
function rozwijanie( object )
{ if (ie4) {
roller= document.all(object);
if (roller.style.display == "none")
{ roller.style.display = ""; }
else
{ roller.style.display = "none"; } }}
//-->
</SCRIPT>

I've heard about function ondecoration but I don't know how to put that in code...

If we are taslking about for links then it is just CSS.

a { text-decoration: none; }
a:hover { text-decoration: underline; }

No it isn't link, so it's impossible to do that by CSS. I have to make it on js. I know that is possible, but I can't find information about it anywhere...

Hmm I see what you mean.

onMouseOver="this.style.text-decoration='underline'"

doesn't do anything.

Ah it's worded differently

onMouseOver="this.style.textDecoration='underline'" onMouseOut="this.style.textDecoration='none'"

that works. Google is your friend