What's this thing called? Mouse pointer displays little yellow box with text inside.

I am using Firefox. When I move my mouse arrow up to the reload current page button, a yellow rectangle displays next to my mouse arrow that says reload current page.

What is this yellow message thing called?

Can I do this to my web pages with CSS?

Thanks.

 

That is "Link Title Attributes".

Setting the attribute on a link allows user agents (visual and non-visual) to tell users about the nature of the linked resource.

NO, you need to add this in your anchor tag within your html.
For example,
<a href=”some link” title=”More posts by Mitchell”>Mitchell</a>

I have highlighted with bold. Hope this helps.

 

Thanks.

I guess it only works on links.