An email being sent out to all Twitter users reads, “Over the coming weeks, we will be making two important updates that will impact how you interact with Twitter applications.”

There are over 250,000 applications built using the Twitter API including desktop apps such as TweetDeck, Seesmic, or EchoFon, websites like TweetMeme or Topsy and mobile apps like Twitter for iPhone and Twitter for Blackberry.

The first update involves new authorisation rules for applications so that all applications will be required to use 'OAuth' to access their Twitter account. OAuth allows applications to access Twitter on your behalf with your approval without asking you directly for your password.

This means that applications are no longer allowed to store your password, so if you change your password, the applications will continue to work. All applications you have authorised will be listed in your settings and you can revoke access to any application at any time.

The second update involves the expansion of Twitter’s link wrapping service, t.co, which wraps links in Tweets with a new, simplified link. These links will include the actual domain and part of the URL “so that you know what you are clicking on” says Twitter.

Last week Twitter announced it was releasing several other new features for the social networking app.