I'm trying to write an iphone web app displaying info from a small ish database while offline. Is it possible to prepare a db and download that rather than downloading the data in some other format and creating it on first use?
if i have to create db, what would be a good format (is there eg compressed xml?) to send data?
is there a maximum storage limit for local dbs?
You could either store it as a large chunk of XML, using HTML 5 Storage, or as a database using Web Database Storage - plain storage is better suported by web browsers (Latest Firefox only seems to suppor the former, for instance).
Secondly, there is no size limit defined in the HTML 5 standard - it simply states:
User agents should limit the total amount of space allowed for storage areas.
For more information, have a look at the HTML 5 Reference, or at these demos.