What does the # sign mean or do? Why don't we use it before a link?

Hi there! The # is used both in HTML and CSS to identify an "id". Because a webpage can only have one id named the same thing we can use it to reference something in particular. For example, you may not have two <div> elements with the id "main-content". Only one element may have that id at a time.

That being said, the #top and #bottom are generally recognized by default by most browsers (for the time being). That could change with upcoming versions of HTML. But the idea here is that you can divide a webpage into different sections and link to those sections within the same page.

Imagine for a moment that you had several divs and you wanted the navigation at the top of your page to take you to that section of the page instead of an entirely different page. This brings up a different use of the <a> tag than you may have seen before.

But you could have something like this:

<!-- this is the "anchor" and sets the point to go to when the href asks for "past-projects" -->
<a name="past-projects"></a> 


<!-- this is the link that that will cause it to jump to the section where the above anchor appears -->
Click <a href="#past-projects">here</a> to view my past projects.

Hope this helps!