The Screen object contains info on screen resolution:
screen.width
screen.height
screen.availHeight
screen.availWidth
The example Maglor mentioned, will make the the background
distort. I don't know what is most important, to keep the background undisturbed or show the whole background image or if it is okay to resize the window to an accurate
proportion of width and height.
Here is an example with javascript
made for InternetExplorer. It forces resizing of window
to adapt the height to the width selected by the user:
(NB DO NOT PREWIEW IN 1st Page!)
<html>
<head>
<title>Stretchy background</title>
<style>
body{ margin:0px;}
h1{color:red; text-align:center;}
.stretchy{
position:absolute;
width:100%;
z-index:-1;
}
</style>
<script>
var z;
function init(){
z=bg.offsetWidth/bg.offsetHeight;
adjust();
}
function adjust(){
var b=document.body
var width=b.offsetWidth;
var height=b.offsetHeight;
var newHeight=width/z;
self.resizeBy(0,newHeight-height)
}
// Do not prewiew in 1st Page, as it will hang!
// 1stPage dont like it's prewiew window
// to be resized by scripting.
</script>
</head>
<body scroll=no onresize="adjust()" onload="init()">
<img id="bg" class="stretchy" src="backgroundImage.jpg">
<br>
<br>
<h1>Heading</h1>
</body>
</html>
GDS