scrollHeight在IE和FF下的区别

/**
 *调整滚屏出现的弹出div位置差别的现象，这个只在IE下才有，在ff下不用调整
 */
function getScollTop(){
    var eleHeight;
    if(document.documentElement){
        eleHeight = document.documentElement.scrollHeight-document.documentElement.clientHeight ;
    }else{
        eleHeight = document.body.scrollHeight-document.documentElement.clientHeight ;
    }
    return eleHeight>0?eleHeight:0;
}