Does gwan support SSI or there is another way to merge different HTML data ?
I'm not sure it's the best way, but I want to include static HTML data into another HTML files ... What do you use if SSI is not working?
SSI can be archived by G-WAN's Dynamic buffers API: simply replace a HTML comment with your partial HTML content.
Use xbuf_frfile() to load your HTML templates. Use xbuf_repl() to "include" the partial HTML to your host page.
See contact.c from G-WAN samples.