function menu(a){
	document.getElementById("b_"+a).style.backgroundImage = 'url(../Content/images/btn_'+a+'_on.jpg)';	
}

$(document).ready(function(){
  $.preloadCssImages();
  $("a[rel^='prettyPopin']").prettyPopin({
			modal : false, /* true/false */
			width : false, /* false/integer */
			height: false, /* false/integer */
			opacity: 0.7, /* value from 0 to 1 */
			animationSpeed: 'fast', /* slow/medium/fast/integer */
			followScroll: true, /* true/false */
			loader_path: '../Content/images/prettyPopin/loader.gif', /* path to your loading image */
			callback: function(){} /* callback called when closing the popin */
		});
});