var clickedflag = "";
$(document).ready(function() {
    $('.menu').hover(function() {
        $(this).attr("src", "/Content/images/" + $(this).attr("id") + "_01.gif");
    }, function() {
        if (clickedflag != "" + $(this).attr("id") + "") {
            $(this).attr("src", "/Content/images/" + $(this).attr("id") + "_00.gif");
        }
    });
});