Webservers generally do not have GPUs. CPUs are completely useless, and GPUs are unprofitable.
CPUs are
*not* completely useless if you mine the right coin.
The server owner/host will likely terminate your service as bitcoin mining is stressful on hardware.
And (as is usually the case for efficiency reasons) running multiple web servers at once isn't?
Webservers do not allow long-standing requests. A limit anywhere from 5 to 30 seconds is not unheard of, and in that case mining will have to start, and restart, and restart, and restart, ad infinitum.
This is a valid point.
Have you considered using your server to provide services/sell goods for BTC instead?
This will usually bring in quite a bit of profit, though things like this are very hard to code.
Anyway, some servers that allow long-running requests (JSP/jetty services are more flexible in my experience) would allow you to theoretically mine if you adapted Java-based miner code(Diablominer or so) to be started by a servlet.
This is possible, but Java is...slow, to say the least.
Matthew:out