Google's always been a company willing not only to try things, but to fail in public. You can go to Google Labs and try all sorts of new services the company's engineers have developed, but that aren't yet ready for mass consumption. Starting today, Google is applying that approach to Gmail.

Click "Settings" in Gmail, and you should see a Labs tab.(The company started rolling out the change at 6 p.m., but said it could be hours or days before every Gmail user has it.) Within the Gmail lab are 13 tweaks, from a change in the way your signature appears at the end of messages to an expanded way to mark messages to a setting called "Email Addict" that lets you block Gmail and Chat for 15 minutes so you can walk away and have a life.

I haven't had much chance to play with the new tweaks, but these look the most useful to me:

Superstars: Standard Gmail lets you add a yellow star to an important message. Enabling Superstars let's you mark messages with different colored stars and other icons like a check mark or exclamation point. You choose which icons you want to use. Should be useful for prioritizing and sorting messages.

Quick Links: A way of bookmarking any page within Gmail. You can link to an individual email message, obviously, but you can also do a search and bookmark that search. Go back to it again and the link will display any new messages that fit the search criteria. You can do the same thing with browser bookmarks, but this looks to be easier, plus the links display within the Gmail interface.

Signature Tweaks: Let's you put your automated signature above the quoted text when you respond to a message, instead of all the way at the bottom of what somebody else wrote.

My nominations for least useful:

Email Addict: Taking a break from email's a great idea, but this is unlikely to get many people to do that. You click a link at the top of the window and are locked out of your account for 15 minutes. But you can get back in to your account anytime you want, just by refreshing the page.

Random Signature: Appends a random famous quote to the end of your email. I'll say this: They can't be more annoying than the quotes people choose for themselves.