function isrefresh()
{ 
//window.location.href = window.location.href;

}
function document.onkeydown()
{
if(window.event.keyCode=='116')
{
window.event.keyCode=0;
window.event.returnValue=false;
}
}
function document.onkeyup(){
var tag =false;
if(window.event.keyCode=='116'){
isrefresh();
}
}