This service is being provided as a convenience to users who need to be able to produce a small DOS program and do not have access to a DOS machine with a compiler on it. There is no guarantee that this service will be available in the future, and I reserve the right to disable it when I need the CPU cycles myself.

There is currently a limit of 1000 source bytes and 200,000 executable bytes. Only C programs are allowed. The math library will be linked in. Symbol information will be stripped. If compilation is successful, all you will get is the binary (exe format), else you will see the results of your compilation.
Code:

http://www.delorie.com/djgpp/compile/