I just noticed an apparently-new warning in the "Mobile crawl errors" section of Google Webmaster Tools. It reports that two pages on my main (non-mobile) Web site are too big for common mobile devices, with the error message "Document size too large". These two pages are quite a bit bigger than all the others, so I cannot tell where Google's cut-off is for determining that a page is "too large" for mobiles, but it is somewhere between 21kB (Size O.K.) and 30.3kB (Size too large).
Unlike other errors and warnings I've seen, there's no icon next to the warning to click to see the documentation for this error, so I guess they haven't documented it yet.
The good news is that I limit my mobile-device pages to 17.5kB, well under their threshold... :)
Jim
