>> I would like to know if it's possible to set options in Composr to control how much resource it takes up. For example, if it uses up more than a defined threshold, it will throttle it or break the connection, whichever is chosen in the options. Throttling may make the site run slower, but it would lessen the chance of Composr causing issues with using too much resource on my web hosting provider, resulting in possible account suspension.

That's not really viable.

>> missing image dimension specifications

This would be client-side performance not server performance. v10 will include this in more key spots though.

>> defining a longer expiry time for browser cache (maybe a week instead of a few hours)

You can configure rules in .htaccess, and you can set up the bot/guest cache (our tut_optimisation tutorial should cover it, or just run /config_editor.php and turn it on).

>> removing question marks in some requests in order to allow cache services to cache them, etc

Caching actual pages for logged in users is not viable, these need to be dynamic so as to represent accurate dynamic information (simple examples - list of online users, or number of points you have, or relative dates).

>> using CSS sprites

These are a maintenance nightmare. v10 will use base64 encoding for some files which is much easier to maintain.

>> I'm finding it a problem that Composr is using up too much resource usage, and my site isn't even that big. I only get a few users every now and then. I appreciate the considerations.

This really shouldn't be the case unless the host is really over-subscribed or you're on a dirt-cheap plan. A request might take 1 second of CPU time on a slow server, so you can imagine it would take many thousands of users browsing the site to truly use up a server's capacity. Even if you only have 5% of a server's resources it's still over 100.

Anyway, you might find some good ideas in tut_optimisation, and we are making many improvements in v10.

Guest cache is probably the best thing, so look into that. If you're getting flooded with bots, the guest/bot cache helps greatly.

I'll check in to those. Not much I can do on a shared hosting platform though, and I suspect it's a problem rather than high traffic because it was a rather sudden problem.

I suspect it might be SSL causing the high loads. I disabled SSL for now and will be monitoring usage.