I'm assuming class="tduser" has some width styling, i'll pretend widh:50px. If these assumptions are wrong then please explain more of what you want.
you could always change the classname on mouseover. And have CSS display it another way.
so user the mouseover to rewrite the dom classname which will trigger a display change: Here are the basic parts.
div.tduser { width: 50px; }
div.tduser_full { width: auto; }
onmouseover="javascript:showUserFull()"
onmouseout="javascript:showUserPart()"
function showUserFull()
{
this.classname = 'tduser_full';
}
function showUserPart()
{
this.classname = 'tduser';
}