var winWidth = 0;
var winHeight = 0;  
function findDimensions() //函数：获取尺寸  
{  //获取窗口宽度  
if (window.innerWidth)  
winWidth = window.innerWidth;  
else if ((document.body) && (document.body.clientWidth))  
winWidth = document.body.clientWidth;  //获取窗口高度  
if (window.innerHeight)  
winHeight = window.innerHeight;  
else if ((document.body) && (document.body.clientHeight))  
winHeight = document.body.clientHeight;  //通过深入Document内部对body进行检测，获取窗口大小  
if (document.documentElement  && document.documentElement.clientHeight && document.documentElement.clientWidth)  
{  
winHeight = document.documentElement.clientHeight;  
winWidth = document.documentElement.clientWidth;  
}  //结果输出至两个文本框  
//document.form1.availHeight.value= winHeight;  
//document.form1.availWidth.value= winWidth;  
//alert(winHeight); 
return winHeight;
}  


//获取尺寸海曙结束

function SetMiddle()
{var Sheight=(findDimensions()-703);//
    if(Sheight>0){
        document.body.style.marginTop=Sheight/2+"px";
    }
}