$(document).ready(function() {	
	function isset () {
	    // http://kevin.vanzonneveld.net
	    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
	    // +   improved by: FremyCompany
	    // +   improved by: Onno Marsman

	    var a=arguments, l=a.length, i=0;

	    if (l===0) {
	        throw new Error('Empty isset'); 
	    }

	    while (i!==l) {
	        if (typeof(a[i])=='undefined' || a[i]===null) { 
	            return false; 
	        } else { 
	            i++; 
	        }
	    }
	    return true;
	}
	var curr = '';
	
	$(".rollover").hover(
		function() {
		  	curr = $(this).attr('src');
			ext = curr.substr(curr.lastIndexOf('.'),4);
			overlen = curr.length;
			over = curr.substr(0, overlen-4);
			over = over+'_o'+ext;
			$(this).attr({ src: over});
		},
		function() {
			if (isset(curr)) {
				$(this).attr({ src: curr});
			}
		}
	);

	$(".rollover").each(function(i) {
		temp = this.src;
		ext = temp.substr(temp.lastIndexOf('.'),4);
	  	prelen = temp.length;
	  	pre = temp.substr(0, prelen-4);
	  	pre = pre+'_o'+ext;
	  	preload_image_object = new Image();
	  	preload_image_object.src = pre;
	});
	
	
	$('.alt_rollover').each(function() {
		var over = $(this).attr('longdesc');
		preload_image_object = new Image();
	  	preload_image_object.src = over;
	});
	
	$(".alt_rollover").hover(
		function() {
		  	curr = $(this).attr('src');
			var over = $(this).attr('longdesc');
			$(this).attr({ src: over});
		},
		function() {
			if (isset(curr)) {
				$(this).attr({ src: curr});
			}
		}
	);
});