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;
}