Re: expires (was: lynx-dev cache control)

[David Woolley]

> This is from the 4.01 specs:
> ======
>    The following sample META declaration:
> <META http-equiv="Expires" content="Tue, 20 Aug 1996 14:25:27 GMT">
> 
>    will result in the HTTP header:
> Expires: Tue, 20 Aug 1996 14:25:27 GMT
> ======
> 

This is only true of web servers that understand the true meaning of
META.  I don't know any that do, although I'm sure they exist.  You can
safely assume that most people who put in such META tags are doing so
on non-META-aware servers.  Most people use these because they are not
allowed to set the meta data properly or only have a vague idea that
HTTP exists at all and there might be more to configuring a server than
supplying HTML and GIFs.

The result of not setting the header is that intermediate proxies will
ignore the caching directives and cache based only on the headers.

Also, HTTP Cache-Control headers will work on non HTML resources, so
you still need to be able to configure the meta data by out of band
means.  As an aside, the non-approved Refresh: header will also work
at the HTTP level for the big 2, allowing self refreshing GIFs, etc.

The big 2 browsers will act on the META lines, even though they probably
shouldn't, but, in any case, cache liberally.