resolution reading ...

My site is best viewed at 1024*768 resolution.

At the opening page there is an alert that says "Site best viewed at 1024*768 resolution", then a 6 second timeout, and finally redirects to main page.

How can I first get their screen-resolution, then either redirect if it is 1024*768, skipping the alert; but if its not then alert and redirect?

<script>
if(screen.width == 1024)
{
window.location='b.htm'
}
else
{
setTimeout('window.location = "b.htm"',6000)
alert('best viewed')
}
</script>

something like this