Override Onmouseover In A Class, Now I Can't Get My Class Attributes.

I'm currently working with Javascript to build some "dynamic" tabs. Basicly, the tab "onmouseover" and "onmouseout" event have been overriden to change the tab's css class.

Here's the class:

function HtmlTab(id)
{
this.id = id;
this.tab = document.getElementById(id);
this.cssover = "over";
this.cssout = "out";

this.tab.onmouseover = function()
{

this.className = this.cssover; // NOT WORKING
}
this.tab.onmouseout = function()
{
this.className = "gen";
}
}
My problem is, I cannot access my HtmlTab class attributes from the this.tab.onmouseover function.

Anyone knows a way to fix this?