Question: Can someone tell me, what the href with the "#" means?

```
<a id="logoutLink" href="#">Logout</a>

```

Answer: 
It is the shortest way to say "go nowhere" :)

Often something else is bound to that link, a javascript event handler in most cases. But if an `<a>` doesn't have a `href`, most browsers don't render it with the same styling...so you need a short something to put there.

If it had something following the hash, like `<a href="#topics">Go to Topics</a>` it is a scroll to link, it goes to where the element with `id="topics"` is at the top of the page. A common example is `<a href="#top">Go to Top</a>`, and you stick a `<div id="top"></div>` at the very top of the page.
If points to an anchor on the page. In this case the anchor is just default. You could have multiple anchors on the page 

<a name="anchor1"></a>
<a name="anchor2"></a>
<a name="anchor3"></a>

and link to them as

<a href="#anchor1">link 1</a>
<a href="#anchor2">link 2</a>
<a href="#anchor3">link 3</a>