$(document).ready(function() {

	if ($('div#navigationPortfolioLayer').length > 0) {
		// image loading
		$('div#navigationPortfolioLayer a img').preload({
			find:'_off.gif',
			replace:'_on.gif'
		});
		//image rollover
		$('div#navigationPortfolioLayer a img').not('div#navigationPortfolioLayer a.actClass img').hover(function(){
			this.src = this.src.replace('_off.gif','_on.gif');
		},function(){
			this.src = this.src.replace('_on.gif','_off.gif');
		});
	}

});