enconttre este post en el buscador :) gracias reposteo el script por que el original parece que se malogró:
Código HTML:
<script language="JavaScript">
if (screen.width + "x" +screen.height == "800x600"){
document.write ("<b>800x600</b>")
}
if (screen.width + "x" +screen.height == "640x480"){
document.write("<b>640x480</b>")
}
if (screen.width + "x" +screen.height == "1024x768"){
document.write("<b>1024x768</b>")
}
</script>