function fixheight(){
    try{
        var size = getPS();
        var elem = document.getElementById("win_fill")
        if(size.height < 800) elem.style.height = "800px"; 
        else elem.style.height = size.height + "px";
    }catch(e){
        document.getElementById("win_fill").style.height = "800px"; 
    }
}

function getPS() {
    var myWidth = 0, myHeight = 0;
    if(typeof(window.innerWidth) == 'number') {   
        myWidth = window.innerWidth;  
        myHeight = window.innerHeight;
    }else if(document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight )) {  
        myWidth = document.documentElement.clientWidth;  
        myHeight = document.documentElement.clientHeight;
    }else if(document.body && ( document.body.clientWidth || document.body.clientHeight ) ) { 
        myWidth = document.body.clientWidth;  
        myHeight = document.body.clientHeight;
    }
    return {width:myWidth,height:myHeight};
}

fixheight();
window.onresize = fixheight;