This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
The <html:base/> tag puts an absolute reference to the jsp page generating it.
This is then used when using relative urls in the jsp so that the location of the resource you might want to include is calculated based on the location of the jsp instead of the contents of the request uri.