I am trying to get a page to display specific properties depending on whether or not a specific cookie is set... I am trying this

 var x = readCookie('age');
window.onload=function(){
if (x='null')  {    
      document.getElementById('wtf').innerHTML = ""; 
   };
if (x='over13')  {    
      document.getElementById('wtf').innerHTML = ""; 
   };
if (x='not13')  {    
   document.getElementById('emailBox').innerHTML = "<style type=\"text/css\">.formError {display:none}</style><p>Good Bye</p><p>You must be 13 years of age to sign up.</p>"; 
   };

   }

It always just defaults to whatever is in the first if statement... I am still learning my javaScript so I am sure this is sloppy.. can someone please help me get this working?