Resolution Check Script then write

I need a script that checks resolution and if the resoulution is 800by 600 it will insert image a
if resultion is 1024 by768 it will insert image b
Any help would be great thanks

Internet search for "resolution sniffer" produced DHTML Shock - Other - Resolution Sniffer (http://www.dhtmlshock.com/other/ResolutionSniffer/default.asp) specifically for 800 x 600 and 1024 x 768 resolutions to redirect with instructions.

I appreciate the post but that isnt what Im looking for.
I need a javascript that will document write based on resolution settings.
I dont know javascript but this is what I want it to do.
If resoultion is 800 by 600 document write (pic url)
If resolution is 1024 by 768 document write (alt pic url)

Ok I have a simpler script that I tested in the three browsers in my sig and at both resolutions.

<SCRIPT LANGUAGE="JavaScript1.2">
<!-- Begin
if (screen.height >= 768 && screen.width >= 1024) {
document.write("<img src='imagea.jpg' width=512 height=384 border=0>");
}
else {
if (screen.height == 600 && screen.width == 800) {
document.write("<img src='imageb.jpg' width=304 height=204 border=0>");
}
}
// End -->
</script>

Just replace the current image tag in your page scripting with the above script changing the imagea.jpg and the width=512 height=384 to fit your "a" image in your root folder for the 786/1024 statement and the same for the 600/800 statement with your "b" image specifications.

Note: Must change your monitor resolution to preview the result as it goes by the real monitors resolution set and not a web editors screen size emulation.

Same script as used for full path url.

<SCRIPT LANGUAGE="JavaScript1.2">
<!-- Begin
if (screen.height >= 768 && screen.width >= 1024) {
document.write("<img src='http://your-web-site-address-here.com/imagea.jpg' width=512 height=384 border=0>");
}
else {
if (screen.height == 600 && screen.width == 800) {
document.write("<img src='http://your-web-site-address-here.com/imageb.jpg' width=304 height=204 border=0>");
}
}
// End -->
</script>

Edit: for small scripting syntax typo.

This is exactly what I had in my head. I knew I saw document write based on resolution in scripts before. FOr isntance "Y our using a 800 by 600 resolution" So i fgured it could be done. Thanks for the help!