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

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

```

Answer: 
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>
The hash symbol (i.e., `<a id="logoutLink" href="#">Logout</a>`) is a placeholder, so that you can preview the "Logout" link in a browser as you develop your page. Eventually, the hash symbol will be replaced with a real URL.