JS pop-up layer source compatible with IE, FF, chrome__ compatible

function Showwin (O1,O2) {

var Mask=document.getelementbyid (O1);

var Popwin=document.getelementbyid (O2);

Document.documentElement.scrollHeight in IE, FF, Chrome is to get the full content of the Web page height
Document.documentElement.offsetHeight in IE is to obtain the inner surface of the clientheight (that is, a page does not include the printed debug information), in FF, Chrome to get the full content of the page height

Compatible with different browsers, get the height of the entire page

var maskheight=document.documentelement.offsetheight<document.documentelement.scrollheight? Document.documentElement.scrollHeight:documentElement.offsetHeight;

Let the shroud cover the entire page

mask.style.height=maskheight+ "px";

Document.documentElement.scrollTop in IE get the scroll bar after the top of the height of scrolling, under the chrome, FF get a height of 0
Document.body.scrollTop is zero under IE, Chrome, ff

Compatible with different browsers, the height of the scroll bar from the top

var top=document.body.scrolltop==0?document.documentelement.scrolltop:document.body.scrolltop;

Height of the pop-up layer from the top

popwin.style.top=260+top+ "px";

mask.style.display= "Block";

popwin.style.display= "Block";

}html code omitted