function popupWindow()
{	
	var windowFeatures =    'height=500' + 
							',width=800' + 
							',toolbar=1' + 
							',scrollbars=1' + 
							',status=0' + 
							',resizable=1' + 
							',location=0' + 
							',menuBar=0';

    var windowName = 'About this ad';
	var windowURL = '/aboutad';
	var centeredY,centeredX;
			
	if (jQuery.browser.msie) {
        centeredY = (window.screenTop - 120) + ((((document.documentElement.clientHeight + 120)/2) - (250)));
		centeredX = window.screenLeft + ((((document.body.offsetWidth + 20)/2) - (400)));
	}else{
        centeredY = window.screenY + (((window.outerHeight/2) - (250)));
		centeredX = window.screenX + (((window.outerWidth/2) - (400)));
	}
	window.open(windowURL, windowName, windowFeatures+',left=' + centeredX +',top=' + centeredY).focus();
}

jQuery(function() {
   
   jQuery('.about_ad_popup').bind('click', popupWindow);
   
});