function createXMLHTTPObject ( )
{
	try 
	{ 
		return new XMLHttpRequest(); 
	} 
	catch (error) 
	{
		return false;
	}
}

function sendRequest ( url, callback )
{
	var req = createXMLHTTPObject ( );
	if ( !req ) return;
	
	req.open ( "GET", url, true );
	req.onreadystatechange = function ( )
	{
		if ( req.readyState != 4 ) return;
		if ( req.status != 200 && req.status != 304 ) 
		{
			alert ( "HTTP error " + req.status );
			return;
		}
		callback ( req );
	}
	if ( req.readyState == 4 ) return;
	req.send ( null );
}

function xmlhttp_start ()
{
	/* test mogelijkheid tot ajax: */
	var req = createXMLHTTPObject ( );
	if ( !req ) return;
		
	var e = document.getElementById( 'werknav' );
	if ( !e ) return;
	var links = e.getElementsByTagName ( 'a' );
	for ( var i = 0; i < links.length; i++ )
	{
		links[i].onclick = getPage;
	}

	var e = document.getElementById( 'thumbnails' );
	var links = e.getElementsByTagName ( 'a' );
	for ( var i = 0; i < links.length; i++ )
	{
		links[i].onclick = getPage;
	}
}

function getPage ( )
{
	sendRequest ( this.href, showPage );
	return false;
}

function showPage ( req )
{
	var html = req.responseText;
	var i = html.indexOf ( '<div id="content_werk">' );
	var j = html.indexOf ( '<div id="footer">' );
//	alert ( html.substring ( i + 23, j - 7 ) ) ;
	document.getElementById ( 'content_werk' ).innerHTML = html.substring ( i + 23, j - 7 );

	xmlhttp_start ();	
}	
/*
*/