HTTP HEAD requests for Last-Modified info

Awhile ago, I posted a question re: HTTP requests to obtain Last-Modified
info for web pages. I got answers that indicated the way to get header info
for a theoretical "www.site.com/page.html" would be to open a connection to
www.site.com and issue the following request:

HEAD /page.html HTTP/1.0 <CRLF><CRLF>

This is good in that it does elicit a set of info, but it's bad in that it
does not ALWAYS return Last-Modified info... which is what I really need.

Does anyone know if there is something additional I need to add to the
request to ALWAYS get the Last-Modified info? I've read the spec, but am
not clear on what I need to do.

Thanks,

Stephen Zagerman