Any article page doesn't display correctly, why?

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Hi all,
starting from yesterday something happened...

The problem is that when I try to open an article, any article, the page displayed is the printing page, not the reading .aspx page. The browser displays the pages without any side bar and the bottom comments are in the printing format.

Consider that on my PC here at work I have IE7, Firefox and Safari.

IE7 is the deafult browser. So yesterday, when I detected the problem for the first time, I used Firefox. Then I printed an article. After then also Firefox had the same problem.

This morning I tried with another article from Safari. I printed it and, again, also Safari had the same problem.

What can I do to solve the problem?

Thanks in advance for your help