ACTION-571: Draft text about showing unrelated identity signals

>From the last meeting, in reference to comment #2 from one of the reviewers (http://lists.w3.org/Archives/Public/public-usable-authentication/2009Mar/0001.html) Mez and I came up with the following text for a new section 7.3:

"Browsers SHOULD NOT display security sensitive information for page content which the user is not interacting with. Security sensitive information includes security indicators, dialogs prompting for user credentials, script errors and dialogs."

Please suggest improvements to both wording and content.

Joe Steele