A stupid irritant frame over my desktop

That's right. Since a few days ago, a stupid, thin, black frame shows up over any application I am using, normally on the widow part I am using. For example, now it is framing the box where I am writing this. Other times it frames the first item in the finder or in an web page or the first icon in my desktop, and stay there moving from one side to another and disturbing.

I have a new MacBood Air to which I migrate from another mac 2 weeks ago.

Help please
THANKS!
Antonio

are they black frames around certian commands and buttons.

In that case you may have accidentally turned on a feature that is designed for people with poor eyesight

Go to  menu > system preferences > Universal Access and turn off any disability featues