Changing CSS Style Onmouseover?

So I didn't think this would be very hard, but I keep running into problems.

I have:

function changeCSS(idName, newClass) {
document.getElementById(idName).className=newClass;
}

And then:

<p id="Link1" onmouseover="changeCSS(Link1, '#profileNav .hoverNav');" onmouseout="changeCSS(Link1, '#profileNav p');">Link1</p>

I get the error "Link1 is not defined" though.

Anyone know why this is happening? Or a different way to achieve my main goal which is to change Link1's css class.