web page snapshot (how to?)

/*
Plugin Name: WebSnprX
Plugin URI: http://www.mademyday.de/neu/
Description: WebSnprX simply integrates <a href="http://www.websnapr.com">WebSnapr</a>-Script in your MODx content. Adds preview bubble to all external links.
Version: 0.6 - 03.04.07
Author: Marc Hinse (based on a Wordpress plugin by XSized - http://tagg.selfip.com/blog/wordpress-plugin-snapr/
Author URI: http://www.mademyday.de/neu/
*/

/*
Javascript for Preview-Bubbles by WebSnapr - http://www.websnapr.com
*/

 $e= & $modx->Event;
switch ($e->name) {
	case "OnWebPagePrerender":	
	$text = $modx->documentOutput;
	// search and replace external Links in document	
	        $modx->documentOutput = str_replace('base href="http://','basehref="http://',$modx->documentOutput);
		$modx->documentOutput = str_replace(' href="http://',' class="previewlink" href="http://',$modx->documentOutput);
                $modx->documentOutput = str_replace('basehref="http://','base href="http://',$modx->documentOutput);
		// $modx->documentOutput = str_replace('class="previewlink" href="'.$modx->config['site_url'],'href="'.$modx->config['site_url'],$text);
		break;	

	case "OnParseDocument":
	// generate JS for the header
	
		$WebSnprX_pluginpath = $modx->config['site_url']."assets/plugins/WebSnprX/";
		$SnaprHead = "\n<!-- Snapr Plugin -->\n";
		$SnaprHead.= "<script type=\"text/javascript\">var bubbleImagePath=\"".$WebSnprX_pluginpath ."bg.png\"</script>\n";
		$SnaprHead.= "<script type=\"text/javascript\" src=\"". $WebSnprX_pluginpath ."previewbubble.js\"></script>\n";
		$SnaprHead.= "<!-- /Snapr Plugin -->\n";	
		$modx->regClientScript($SnaprHead);
             break;

	    default:
		return; // stop here - this is very important. 
        break;
}

<p>
<a class="previewlink" class="previewlink" href="http://www.click-immo.com" target="_blank">
www.click-immo.com </a>
</p>