function changeheight()
{

    winH = document.documentElement.clientHeight;
    //alert(winH);
    minus=30;
    winH=winH-minus;
    
    divel=document.getElementById("site");
    
    divH=divel.offsetHeight;
    
    
    if((divH-100)<winH)
    {
    
    divel.style.height = winH+"px";
    }
    
    divHnew=divel.offsetHeight;


}