firefox event is not defined

firefox event is not defined

function    showTip(e){
event    =    window.event    ||    e;
var    div3    =    document.getElementById( 'div3 ');  
div3.style.display =   " block  " ;  
div3.style.left = event.clientX;  
div3.style.top = event.clientY;
div3.style.position =   " absolute  " ;  
}

在FIREFOX中,ENENT要显示的传给函数

onmousemove =   " showTip(event)  "