Maximum web page size in general? iPhone? Android?

I'm designing am HTML 5 WebApp -- will use the local db storage, etc. It is targeted for AppPhones (iPhone and Android), and HTML 5 browsers. (IE and old browsers will get the old version of the site.)

Questions:

• Is there a max download size for iPhone or Android native browsers?
• Any limitations with PC-based browsers?
• I also plan to encourage users to download via开发者_JS百科 WiFi. I'm considering telling people how long the download will take, based on downloading an initial part of the data. Thoughts on that?

Of course, the JS will be minimized, the server will compress.

The download will be JSON, not presentation HTML.

According to a MobileGeo post, iPhone default local db is 5MB. The article says that the data is stored at UTF-16. Maybe I should use JS to locally compress my larger "text" fields in the database?

A 2008 HTML5 spec suggests 5MB as a db default max size per domain.

The current HTML 5 Indexed Database spec makes a reference to storage quota but nothing concrete.

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This question is a bit unclear, but it does remind me of this article about iphone cacheability that states

Reduce the size of each component to 25 Kbytes or less for optimal caching behavior.

(this statement is read in the context of the iPhone's web browser)