Setting up the chrome.manifest file
The chrome manifest is a plain text file used by XULRunner to locate the URI which locates the application resources. The file is responsible for informing the chrome registry of the chrome package names. The chrome registry is a service maintained by the gecko runtime. The registry is used to provide mappings from chrome package names to the physical location of chrome packages.
An example of what would go into this file would be the following:
content myapp file:content/
Note: to find more information about what goes into a chrome.manifest file please visit the following link, Chrome Registration