HTML DOM width + height of visible window

How do I get the current height and width of the available space in the browser as it is open.

I don't want the height of the total document, just what's visible on the screen.

You can take a look at this blog post to see the method.

and in short in give that code

function alertSize() {
    var myWidth = 0, myHeight = 0;
    if(typeof(window.innerWidth) == 'number') {
        // Non-IE
        myWidth = window.innerWidth;
        myHeight = window.innerHeight;
    } 
    else if(document.documentElement && (document.documentElement.clientWidth || document.documentElement.clientHeight)) {
        // IE 6+ in 'standards compliant mode'
        myWidth = document.documentElement.clientWidth;
        myHeight = document.documentElement.clientHeight;
    } 
    else if(document.body && (document.body.clientWidth || document.body.clientHeight)) {
        // IE 4 compatible
        myWidth = document.body.clientWidth;
        myHeight = document.body.clientHeight;
    }

    window.alert( 'Width = ' + myWidth );
    window.alert( 'Height = ' + myHeight );
}

also have to be noted that most of js framework (jquery, ext, prototype) would provide a function for doing that (IMHO).

in jQuery:

$(window).width();
$(window).height();