$(document).ready(function() {
	$("#nav a").hover(
				// over
				function(){
					// store the original image src
					$(this).children(":first-child").attr( "originalsrc" , $(this).children(":first-child").attr("src") );
					
					// add -over to the image unless it is already -over
					if (!$(this).children(":first-child").attr("src").match(/-over/) ) {
						$(this).children(":first-child").attr( "src", $(this).children(":first-child").attr("src").replace(/\./, "-over.") );
					}
					
				},
				
				// out
				function(){
					// replace the original src
					$(this).children(":first-child").attr(
						"src", $(this).children(":first-child").attr("originalsrc")
					);
					
					$(this).children(":first-child").attr(
						"originalsrc", null
					);
				}
			);

});


window.onload = function() {
	// preload
	$("#nav a img").each(
		function() {
			$("<img>").attr( "src", $(this).attr("src").replace(/\./, "-over.") );
		}
	);
}