// main nav mouse over animation
$(document).ready(function() {

  $("#top_nav li").prepend("<span></span>"); //Throws an empty span tag right before the a tag

  $("#top_nav li").each(function() { //For each list item...
    var linkText = $(this).find("a").html(); //Find the text inside of the <a> tag
    $(this).find("span").show().html(linkText); //Add the text in the <span> tag
  }); 

  $("#top_nav li").hover(function() {  //On hover...
    $(this).find("span").stop().animate({
      marginTop: "-40" //Find the <span> tag and move it up 40 pixels
    }, 250);
  } , function() { //On hover out...
    $(this).find("span").stop().animate({
      marginTop: "0"  //Move the <span> back to its original state (0px)
    }, 250);
  });

});