force certain options values for Firefox.
document options values for Firefox.
Revert "document options values for Firefox."

This reverts commit 9d0582754383c2cb87ac6d12fd0d6114ca0aff99.
Revert "force certain options values for Firefox."

This reverts commit 11e781e6ac307ce9faf56a37c3ccca5ebefa5a33.