$(document).ready(function() {

		 $("#twitter").hover(
				  function () {
				$("#twitter-img").attr({src: "images/twitter_up.jpg"});

				  }, 
				  function () {
				$("#twitter-img").attr({src: "images/twitter_down.jpg"});
				  }
				);
				 
				  
				$("#facebook").hover(
				  function () {
				$("#facebook-img").attr({src: "images/facebook_up.jpg"});

				  }, 
				  function () {
				$("#facebook-img").attr({src: "images/facebook_down.jpg"});
				  }
				);
		});