js获取浏览器显示区域高度
document.documentElement.clientHeight //获取显示区域高度
document.body.scrollTop//获取滚动条高度
document.getElementById("footid").offsetTop//获取元素到浏览器顶端的高度
var s = "网页可见区域宽 ：" + document.body.clientWidth;
s += "\r\n网页可见区域高：" + document.body.clientHeight;
s += "\r\n网页可见区域高：" + document.body.offsetHeight + " (包括边线的宽)";
s += "\r\n网页正文全文宽：" + document.body.scrollWidth;
s += "\r\n网页正文全文高：" + document.body.scrollHeight;
s += "\r\n网页被卷去的高：" + document.body.scrollTop;
s += "\r\n网页被卷去的左：" + document.body.scrollLeft;
s += "\r\n网页正文部分上：" + window.screenTop;
s += "\r\n网页正文部分左：" + window.screenLeft;
s += "\r\n屏幕分辨率的高：" + window.screen.height;
s += "\r\n屏幕分辨率的宽：" + window.screen.width;
s += "\r\n屏幕可用工作区高度：" + window.screen.availHeight;
s += "\r\n屏幕可用工作区宽度：" + window.screen.availWidth;
s += "\r\n 高度：" + document.documentElement.clientHeight;
s += "\r\n 宽度：" + document.documentElement.clientWidth;
