Well someone is requesting some URL's with really strange hex codes.
How can I find out what they are up to. The problem is I don't even know what code that is, it's not a hex code.
How can I find out what's going on here?
If it's definitely not something you'd expect for your application it is entirely possible someone is doing Something Nasty (tm).
Google the URL (or an interesting part of it) and see what you get - As an example, Code Red and Nimda's patterns were published all over the internet, so if you Googled the request you would often find a page talking about the worm that was harassing your (non-Windows) web server.
So, the snippet that you posted in the title translates to, in bytes:
What this means to your web service is completely dependent on how the web server and application handle this input.