$(document).ready(function(){
	$('#menu li a[rel]').mouseover(toggleBackgroundOn);
	$('#menu li a[rel]').mouseout(toggleBackgroundOff);
});

function toggleBackgroundOn(){
	$('.block[rel='+$(this).attr('rel')+']').css('background-position', 'bottom left');
}
function toggleBackgroundOff(){
	$('.block[rel='+$(this).attr('rel')+']').css('background-position', '');
}