There are now two very distinct and different versions of Struts, generally referred to as Struts 1 and Struts 2. Because Struts has been around for many years, when someone says "Struts" without qualifying it, they generally mean Struts 1. When Struts 2 was born, while it kept the concept of a central controller, it departed from Struts 1 in a lot of important ways such as the use of a Servlet filter instead of a Servlet, and a completely different JSP tag library. If you'd like to know more about the differences between Struts 1 and Struts 2, see this link.
Note: Eric put together a handy way to EscapeHtml for posting in the forums
For all other questions, click on the respective links for Struts 1 or Struts 2 below: