A plugin that an application could add to generate application-specific
SEO content. The generated content won't be visible to the end users,
but that will be used by the spider of search engines.
You could specify the class of an implementation of the SEO renderer
as a listener in WEB-INF/zk.xml. For example,
<listener>
<listener-class>com.foo.MySEORenderer</listener-class>
</listener>
Also notice that you could generate JavaScript snippet too, since it will
be interpreted by the browser. For example, if you'd like to inject some JavaScript
code to every page, you could implement this class and register it as a listener.
Notice that the SEO render, if specified, is always called, even if
the crawlable option is not enabled.