This is a adobe acrobat reader plugin for web developers suggestion, its for all browsers since is for the web service that adobe offers, some PDF are already signed with certificate, on the desktop it shows a bar notifyng the user that it does, but on the web there is no information about it, it would be nice to show a panel or a info indicating, the signature, when it was signed, who, and if it's no longer valid, don't make a fuzz about it as it does on the desktop, many documents get signed, time passes and the cert has lost its validity, is not that it wasn't valid, it just expired. Many document expire, there is big difference between expiring and having a invalid from start signature.

The panel could be similar to the desktop one just don't use red on date issues.