function showdiv(id) {
  var ele = document.getElementById(id);
  if(ele != null)
    ele.style.display = "block";
}

function hidediv(id) {
  var ele = document.getElementById(id);
  if(ele != null)
    ele.style.display = "none";
} 

$(document).ready(function(){  
    //Adjust height of overlay to fill screen when page loads  
    $("#dim").css("height", $(document).height());  
   
    //When the link that triggers the message is clicked fade in overlay/msgbox  
    $(".alert").click(function(){  
       $("#dim").fadeIn();
       $("#username").focus();
       return false;
    });  
   
    //When the message box is closed, fade out  
    $(".close").click(function(){  
       $("#dim").fadeOut();  
       return false;  
    });  
   
 });  
   
 //Adjust height of overlay to fill screen when browser gets resized  
 $(window).bind("resize", function(){  
    $("#dim").css("height", $(window).height());  
 });