If you're developing a web application that runs on Linux, and a customer asks for a report in MS Word format, you're going to be in a lot of pain. One approach is buying a Windows licence, installing it in a virtual machine, and hooking up an application to drive it over COM, and then figuring a way to talk to the VM from your web app. A simpler approach is generating a web archive file (.mht) and pretending it's a .doc file. Word happily opens it, usually.
Here's a random helpful tip: try not to have more than 2047 <ul> elements in it, or they'll start spontaneously nesting.