Some Gmail users have started to see messages notifying them of an impending change in the service. The message boasts that "better ads" are coming to Gmail and links to a page explaining the changes.

Basically, ads are going to become more targeted and hopefully more relevant since they will start looking at other signals than until now, notably some of the same ones used to determine whether a message is relevant to the user or not in Priority Inbox.

"With features like Priority Inbox, we’ve been working hard to help sort through the ‘bacn’ in your messages -- the unimportant messages that get in your way," Google writes.

"Soon we’re going to try a similar approach to ads: using some of the same signals that help predict which messages are likely to be important to you, Gmail will better predict which ads may be useful to you," it announced.

The new personalized and improved ads are not here yet, but Google is giving users a heads up. They'll be slowly rolled out and start showing up about a month from now.

Also, Google enables users to disable the feature, though it will be enabled by default. If you decide you don't need or want it, you can simply uncheck the "Show more useful ads by using importance signals from across my messages" option.

Not that you'll want to probably, Google promises to not only make the ads more relevant, but to also serve less of them. If the ads end up getting more clicks, since the users will want to check them out, Google can raise the prices on them and make the same amount of money from fewer ads.

"For example, if you’ve recently received a lot of messages about photography or cameras, a deal from a local camera store might be interesting. On the other hand if you’ve reported these messages as spam, you probably don’t want to see that deal," Google explains how the new targeted ads will work.