Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Useful Printing Tips for a Web-pages in Safari
If you would like to print some Web-content from your Safari browser, but want to make some changes in the way the web-page looks like (for example, delete some pictures and logos) or to limit the quantity of the text information presented on the page by deleting unneeded paragraphs and external links, you are incredibly lucky to be mac user. You can perform all of these actions even without leaving your browser!
As you can see all the advices described afore are quite easy to implement even for the mac dummies. But you need to keep in mind that the changes you will see at your computer screen will be made only for your personal use and all other millions of Internet users will observe the page as it was published originally, without your editing. If this fact makes you feel uncomfortable you can contact the web-page creators and suggest your improvements. Who knows: maybe they will like it.