how to add function to links in css code example

Example: how to add fanctoin to links in css

<!--the frist one turn it red when your mouse on it 
the 2end one get bigger when your mouse on it 
the 3rd one turn ir backround red when your mouse on it 
the 4th chage litte bit (Idk how to explan it)
the 5th underline the link when your mouse on it -->
<style>
a.ex1:hover, a.ex1:active {color: red;}
a.ex2:hover, a.ex2:active {font-size: 150%;}
a.ex3:hover, a.ex3:active {background: red;}
a.ex4:hover, a.ex4:active {font-family: monospace;}
a.ex5:visited, a.ex5:link {text-decoration: none;}
a.ex5:hover, a.ex5:active {text-decoration: underline;}
</style>