this.tooltip = function(elem){  
  /* CONFIG */    
    xOffset = 10;
    yOffset = 20;   
    // these 2 variable determine popup's distance from the cursor
    // you might want to adjust to get the right result   
  /* END CONFIG */    
  $(elem).hover(function(e){                       
    this.t = this.alt;
    this.alt = "";                    
    $("body").append("<p id='tooltip'>"+ this.t +"</p>");
    $("#tooltip")
      .css("top",(e.pageY - xOffset) + "px")
      .css("left",(e.pageX + yOffset) + "px");
      $("#tooltip").show();    
    },
  function(){
    this.alt = this.t;    
    $("#tooltip").remove();
    }); 
  $(elem).mousemove(function(e){
    $("#tooltip")
      .css("top",(e.pageY - xOffset) + "px")
      .css("left",(e.pageX + yOffset) + "px");
  });     
};