There are many ways of doing that.
If you really want to have a 'hover' class in your A element, then you'd have to do:
a.hover:hover { code here }
Then again, it's uncommon to have such a className there, this is how you do a regular hover:
select:hover { code here }
Here are a few more examples:
1
HTML:
<a class="button" href="#" title="">Click me</a>
CSS:
.button:hover { code here }
2
HTML:
<h1>Welcome</h1>
CSS:
h1:hover { code here }
:hover is one of the many pseudo-classes.
For example you can change, you can control the styling of an element when the mouse hovers over it, when it is clicked and when it was previously clicked.
HTML:
<a class="home" href="#" title="Go back">Go home!</a>
CSS:
.home { color: red; }
.home:hover { color: green; }
.home:active { color: blue; }
.home:visited { color: black; }
Aside the awkward colors I've given as examples, the link with the 'home' class will be red by default, green when the mouse hovers them, blue when they are clicked and black after they were clicked.
Hope this helps