Is there an HTML5 local resource quota available?

I am planning to use HTML LocalStorage feature for browsers (especially for FF) to store our application data internally .

I read about it, how to use data isolation for each domain, how a user can increase the quota, etc.

But the question is, does this quota apply? Or does each domain have 5 MB to use?

(*) And, if I need to use, say, 25 MB, and I ask my clients to increase their browser quota, does that mean that all other domains can have this 25 MB available?

Or if another domain is using the entire quota, is there room in my application?

UPDATE:

There is an (additional) question related to browser configuration changes to allow more space (*). Seems like below is a recommended recommendation , does anyone know if this is implemented in FF?

11.3 Disk space

User agents should limit the total amount of space allowed for the storage area, because hostile authors could use this feature to exhaust the user's available disk space.

User agents must protect sites that store data under their origin from other affiliated sites, for example. keeping up to the limit in a1.example.com, a2.example.com, a3.example.com, etc., bypassing the main example .com storage limitation.

User agents can prompt the user when quotas are reached, allowing them to provide more space to the site. ... This allows sites to store many custom documents on the user's computer, for example.

User agents should allow users to see how much space each domain is using.

A basically arbitrary limit of five megabytes per lineage is proposed. Implementation notes are welcome and will be used to update this in the future.

For predictability, quotas should be based on the uncompressed size of the saved data.