Sorry I wasn't clear. I'm thinking of something like this:
echo '<p class="contact-info">';
contact-info.htxt would contain
1234 5th St.<br />
Los Angeles, CA 91234<br />
ph. (310) 555-1234<br />
fax (310) 555-6789<br />
So I'm using extension .htxt to indicate text with html markup, but not a complete well-formed html page. I wondered if there was already an extension established for this purpose.