Page source:

<script type="text/javascript">

function addEngine(path, name, extension, category)
{
	if ((typeof window.sidebar == "object") && (typeof
	window.sidebar.addSearchEngine == "function"))
	{
		window.sidebar.addSearchEngine(
			path + name + ".src",
			path + name + "." + extension,
			name , category);
		alert('Install completed - now select WubHub in the Firefox search bar drop down box, enter your WubHub command and press ENTER');
	}
	else
	{
		errorMsg(name, extension, category);
	}
}

</script>


<a href="javascript:addEngine('http://scharfschuetze.de/', 'WubHubFirefox','png','WubHub Category')">Install WubHub command line in Firefox Search Bar</a>