function add_tag( theform ) {

 // get the form's input
 var resource = theform.resource.value;
 var tag      = theform.tag.value;
 var username = theform.username.value;

 // process the input
 post_tag ( resource, tag, username );

 // cleanup and done
 expand( 'd' + resource );
 return false;

}


function post_tag( resource, tag, username ) {

 // use the input to create a GET request
 var url = './index.cgi?cmd=post_tag&resource=' + resource + '&tag=' + tag + '&username=' + username;

 // create a xmlRequest
 var xmlRequest;
 if ( window.XMLHttpRequest ) { xmlRequest = new XMLHttpRequest(); }
 else if ( window.ActiveXObject ) { xmlRequest = new ActiveXObject( "Microsoft.XMLHTTP" ); }

 // sanity check
 if ( !xmlRequest ) {

  alert( 'Giving up: Cannot create an XMLHTTP instance' );
  return false;

 }

 // give the xmlRequest some characteristics and send it off
 xmlRequest.open( 'GET', url, true );
 xmlRequest.send( null );
 xmlRequest.onreadystatechange = function() {

  if ( xmlRequest.readyState == 4 ) {

   var xmldoc = xmlRequest.responseXML;
   var root_node = xmldoc.getElementsByTagName( 'root' ).item( 0 );
   alert ( root_node.firstChild.data );

  }

 }

}


function expand( id ) {

 var details = document.getElementById( id );
 details.style.display = ( details.style.display == 'block' ) ? 'none' : 'block';

}