Accurate cross-browser viewport width

gistfile1.js

/* ----------------------------------------------- 
 * Accurate Cross-Browser Viewport Width
 * https://gist.github.com/2399828
 * -----------------------------------------------
 * Copyright 2012, Brett Jankord.
 * http://www.brettjankord.com/
 *
 * Licensed under the MIT license:
 * http://www.opensource.org/licenses/MIT 
 * ------------------------------------------------*/
function viewportWidth(){
	var vpw;
 	var webkit = (!(window.webkitConvertPointFromNodeToPage == null));
	
	// Webkit:
	if ( webkit ) {
		var vpwtest = document.createElement( "div" );
		// Sets test div to width 100%, !important overrides any other misc. box model styles that may be set in the CSS
		vpwtest.style.cssText = "width:100% !important; margin:0 !important; padding:0 !important; border:none !important;";
		document.documentElement.insertBefore( vpwtest, document.documentElement.firstChild );
		vpw = vpwtest.offsetWidth;
		document.documentElement.removeChild( vpwtest );
	}
	// IE 6-8:
	else if ( window.innerWidth === undefined ) { 
		vpw = document.documentElement.clientWidth; 
	}
	// Other:
	else{
		vpw =  window.innerWidth;
	}

	return (vpw);
};

// Sample Usage: 
var vpw = viewportWidth();

// Notes:
//----------------------------------------------------------------------------------
// Webkit handles media query widths differntly than most other browsers - read more below
// http://www.456bereastreet.com/archive/201101/media_queries_viewport_width_scrollbars_and_webkit_browsers/ 
// Inspired by the Scott Jehl's expriemnt with getting the visible viewport dimensions
// https://gist.github.com/2051999
// If using respond.js in IE9, the viewport width returned from the code above is no longer accurate
// Be sure to wrap respond.js in conditional comments so it's only used in IE8 and lower as it should be

Decided to turn this gist into a full repo. Repos seem to be more discover-able than gists.