XHTML 1.1 Valid Aligning

An easy XHTML1.1 valid way of aligning divsfunction XHTMLAlign(tagid, align){

var viewportwidth;
var viewportheight;

// the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight

if (typeof window.innerWidth != 'undefined')
{
viewportwidth = window.innerWidth,
viewportheight = window.innerHeight
}

// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)

else if (typeof document.documentElement != 'undefined'
&& typeof document.documentElement.clientWidth !=
'undefined' && document.documentElement.clientWidth != 0)
{
viewportwidth = document.documentElement.clientWidth,
viewportheight = document.documentElement.clientHeight
}

// older versions of IE

else
{
viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
viewportheight = document.getElementsByTagName('body')[0].clientHeight
}

var tag = document.getElementById(tagid);
tag.style.position="absolute";
if(tag.style.marginLeft == ""){
tag.style.marginLeft = "0";
}
if(tag.style.marginRight == ""){
tag.style.marginRight = "0";
}
if(tag.style.marginTop == ""){
tag.style.marginTop = "0";
}
if(tag.style.marginBottom == ""){
tag.style.marginBottom = "0";
}
if(tag.style.width == ""){
if (tag.width != ""){
tag.style.width = tag.width;
} else {
tag.style.width = "0";
}
}
if(tag.style.height == ""){
if (tag.height != ""){
tag.style.height = tag.height;
} else {
tag.style.height = "0";
}
}
if ( align=="left" ){
tag.style.left=parseInt(tag.style.marginLeft) + "px";
tag.style.right= viewportwidth - (parseInt(tag.style.width) + parseInt(tag.style.marginLeft)) + "px";
} else if ( align=="right" ){
tag.style.right=parseInt(tag.style.marginLeft) + "px";
tag.style.left=viewportwidth - (parseInt(tag.style.width) + parseInt(tag.style.marginRight)) + "px";
} else if ( align=="center" ){
tag.style.right= ((viewportwidth - parseInt(tag.style.width))/2) - parseInt(tag.style.marginLeft) + parseInt(tag.style.marginRight) + "px";
tag.style.left= ((viewportwidth - parseInt(tag.style.width))/2) + parseInt(tag.style.marginLeft) - parseInt(tag.style.marginRight) + "px";
}
if ( align=="top" ){
tag.style.top=parseInt(tag.style.marginTop) + "px";
tag.style.bottom= viewportheight - (parseInt(tag.style.bottom) + parseInt(tag.style.marginTop)) + "px";
} else if ( align=="bottom" ){
tag.style.bottom=parseInt(tag.style.marginTop) + "px";
tag.style.top=viewportheight - (parseInt(tag.style.width) + parseInt(tag.style.marginBottom)) + "px";
} else if ( align=="vcenter" ){
tag.style.bottom= ((viewportheight - parseInt(tag.style.width))/2) - parseInt(tag.style.marginTop) + parseInt(tag.style.marginBottom) + "px";
tag.style.top= ((viewportheight - parseInt(tag.style.width))/2) + parseInt(tag.style.marginTop) - parseInt(tag.style.marginBottom) + "px";
}
return;
}


setInterval('XHTMLAlign("divid", "center")', 100);
setInterval('XHTMLAlign("divid", "vcenter")', 100);