What Gmail Notes Does NOT Do
Gmail Notes is called a basic annotation system because it is not an internal feature developed by Google, but instead is implemented by external software that infers the current Gmail conversation from the URL displayed in the Firefox address bar. As such, our app does not have access to your actual Gmail contents. For this reason, Gmail Notes is not, and probably will never be, a slick Web 2.0 application. Nevertheless it does provide a basic annotation feature, which some of us think has been missing from Gmail since the beginning. With that said, there are certain constraints that Gmail Notes users must live with:
You can only use Gmail Notes on Firefox browsers versions 3.6 and later. Although we have considered adding support for Gmail Notes on Google Chrome, right now there are no specific plans to do that. (The major obstacle is the limited user interface options available to Chrome extensions.)
Because Gmail Notes is a separate service, you must sign into Gmail Notes separately from signing into Gmail. Fortunately, the Gmail Notes sign-in page has a "remember me" option, so you won't have to do this every time on a trusted system.
In Gmail "threadlist" views, such as the Inbox, Starred, and Sent Mail pages, there is no way for Gmail Notes to know what conversations are displayed in the current page. For this reason, our software cannot highlight or in any way indicate which items in the list have existing notes. That is why we strongly recommend users manually identify those messages using the Gmail Superstars feature.
There is also no way for Gmail Notes to find out when a conversation is deleted. So if you delete a conversation without deleting the note attached to it, that note will essentially be "lost" in the Google cloud.