When I'm installing libxul-dev I end with this error message:
$ sudo apt-get install libxul-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package libxul-dev is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package libxul-dev has no installation candidate
How can I solve this?

sources.listresemble this? – sr_ Nov 19 '11 at 14:31