Determining a Browser’s Dimensions with Javascript

This is about as cross-browswer compatible as you can get:

<script type="text/javascript">
    var winW, winH;
    if (self.innerWidth) {
        winW = self.innerWidth;
        winH = self.innerHeight;
    } else if (document.documentElement && document.documentElement.clientWidth) {
        winW = document.documentElement.clientWidth;
        winH = document.documentElement.clientHeight;
    } else if (document.body) {
        winW = document.body.clientWidth;
        winH = document.body.clientHeight;
    }
</script>