Thanks for replying Yannick, you are always so quick!
I would like an option to “clear all” active categories. After that a person can single out his own category as active.
So in my example… people would be able to click a button to make all categories passive and then click on the “math” category to only see math-websites. Still above are the other categories, but they are passive.
I think this would still be elegant, fast and you don’t need to make a lot of different pages/menu’s etc. Or am I wrong?