var getZip = function( zipcode )
{
   var req;
   if( !zipcode.match( /^\d\d\d\d\d$/ ) )
   {
      return;
   }

   try
   {
      req = new XMLHttpRequest();
   }
   catch( e )
   {
      try
      {
	 req = new ActiveXObject('Msxml2.XMLHTTP');
      }
      catch( e )
      {
	 try
	 {
	    req = new ActiveXObject('Microsoft.XMLHTTP');
	 }
	 catch( e )
	 {
	    alert( "Can't create XMLHTTP object. Giving up!" );
	    return false;
	 }
      }
   }

   //if( req == null ) { req = new ActiveXObject('Microsoft.XMLHTTP'); }
   //if( req == null ) { req = new ActiveXObject('Msxml2.XMLHTTP'); }

   //req.overrideMimeType('text/plain');

   //req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
   req.onreadystatechange = function() { handleZip( req ); };
   //req.open( "POST", "zip.php", true );
   req.open( 'GET', 'zip.php?zip=' + zipcode, true );
   //req.send( "zip=" + zipcode );
   req.send( null );
};

//var handleZip = function( content )
var handleZip = function( r )
{
   //if( req.readyState == 0 || req.readyState == 4 )
   if( r.readyState == 4 )
   {
      var zb = document.getElementById( 'enterzip' );
      zb.innerHTML = r.responseText;
   }
};