I have noticed that the static_html_cache respects when browsers request a page for different languages / locale. To test things out I viewed my site using different browsers.

Internet Explorer 7 created this file in the cache:
index1.html

Firefox and Opera created this one:
index_1_en_US.html

Is there a way to tell Zenphoto to ignore language when caching files? I am only using English on my site, and I like to avoid doubling up every page in the cache.

Actually both should have created the en_US ones... Don't know why IE does somethign different. There is no way to ignore that to keep in line with multilingual usage.

I have done some snooping on the HTTP headers sent by the different broswers:

IE7:
Accept-Language: en-au
Firefox:
Accept-Language en-gb,en;q=0.5

I then went into 'internet options' > 'languages' then added 'English (United Kingdom)' and 'English (United States)'. My IE7 headers are now:
Accept-Language: en-au,en-GB;q=0.7,en-US;q=0.3

After this change now IE7 is using the same cached files and Firefox and Opera.

In Zenphoto Admin > General my language was set to 'HTTP Accept Language'. For a second test I undid my IE7 browser language changes, and changed my Zenphoto language to 'English (United States)', and now all browsers are using the same cache files. I presume when Zenphoto finds a language it does not recognise (Australian English in this case) in the HTTP headers, it defaults to nothing, hence the filenames I saw.

Zenphoto only recognizes languages that have translations, otherwise it should indeed use the plain (US) English.