When you create an application with GWT and Gear (http://code.google.com/p/gwt-google-apis/), a manifest has to be created to manage offline content.
To minimize the manifest management (and the downloading process) a dedicated manifest has to be created for each browser.
A solution is to use a ServletFilter. This filter will automaticaly return the manifest regarding user's browser.
The filter configuration manages manifest version and resources to be included in the manifest (.css, .html, .gif...).
This filter will only be trigged when the manifest file is requested by Gears.
I hope this solution can help..
Don' t hesitate to post any comments or modifications.