var time = 300; 
var h = 0; 
function addCount() 
{ 
    if(time>0) 
    { 
        time--; 
        h = h+5; 
    } 
    else 
    { 
        return; 
    } 
    if(h>300)  //高度 
    { 
        return; 
    } 
    document.getElementById("ads").style.display = ""; 
    document.getElementById("ads").style.height = h+"px"; 
    setTimeout("addCount()",30); 
} 
window.onload = function showAds() 
{ 
    addCount(); 
    setTimeout("noneAds()",20000);  
} 
var T = 300; 
var N = 300; //高度 
function noneAds() 
{ 
    if(T>0) 
    { 
        T--; 
        N = N-5; 
    } 
    else 
    { 
        return; 
    } 
    if(N<0) 
    { 
        document.getElementById("ads").style.display = "none"; 
        return; 
    } 
    document.getElementById("ads").style.height = N+"px"; 
    setTimeout("noneAds()",30); 
}