function windowHeight() //函数：获取尺寸   
{
//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;
    }
//结果输出至两个文本框
    return ( winHeight );
}
function isFF() {
    return (navigator.userAgent.indexOf("Firefox")!=-1);
}
window.onload = function(){
    wrapper = $('.body .wrapper').height();
    
    html = windowHeight();
    header = $('.header').height();
    footer = $('.footer').height();
//    alert(html + '-' + header + '-' + footer + ' should be ' + wrapper);
    if (wrapper < html - header - footer) {
        $('.wrapper').height(html - header - footer - (isFF()?20:0));
    }
    
};