//from http://andylangton.co.uk/articles/javascript/get-viewport-size-javascript/

function getViewportDimensions() {
	
	var viewportwidth;
	 var viewportheight;
	 
	 // the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
	 
	 if (typeof window.innerWidth != 'undefined')
	 {
		  viewportwidth = window.innerWidth,
		  viewportheight = window.innerHeight
	 }
	 
	// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
	
	 else if (typeof document.documentElement != 'undefined'
		 && typeof document.documentElement.clientWidth !=
		 'undefined' && document.documentElement.clientWidth != 0)
	 {
		   viewportwidth = document.documentElement.clientWidth,
		   viewportheight = document.documentElement.clientHeight
	 }
	 
	 // older versions of IE
	 
	 else
	 {
		   viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
		   viewportheight = document.getElementsByTagName('body')[0].clientHeight
	 }
	 
	 return [viewportwidth, viewportheight];
	 
}
//document.write('<p>Your viewport width is '+viewportwidth+'x'+viewportheight+'</p>');