$(document).ready(function(){

//Add the active class (highlights the very first list item by default)

	$(".m_nav ul li:first-child").addClass('active');
	
//Add the active class if the li item is clicked, or else remove it.

	$(".m_nav ul li").click(function(){
        $(".m_nav ul li.active").removeClass("active");           
        $(this).addClass("active");                                      
    	 return false;                                                          
		}); 
 
});