Java and .NET are two languages targeted at removing platform dependence. This is achieved by adding a virtual machine/framework between the code and the OS.
So, what is the point in using it on the server side, as all websites are accessible via browser, and that is platform independent? Is there any special reason for using them?
.NET is meant for the Windows platform only. Java is the only one of the two that is meant to be platform independent.
These languages have a strong presence on the server end for many reasons: