Question: Let's say I want that every time the user click any link an alert pops up that says "hohoho". 
Do I need to add `onclick="alert('hohoho')"` to every link or can I set this with CSS so that it works with every link?

Answer: 
You could do it with jQuery.

```
$('.myClass').click(function() {
  alert('hohoho');
});

```
It can't be done via CSS as CSS only changes the presentation (e.g. only Javascript can make the alert popup). I'd strongly recommend you check out a Javascript library called [jQuery](http://jquery.com/) as it makes doing something like this trivial:

```
$(document).ready(function(){
  $("a").click(function(){
    alert("hohoho");
  });
});

```