You need to explain when you want the underline. I don’t believe a:active {text-decoration: underline;} would do anything. Your initial post (and my example) mentioned a:hover which is different, so please clarify.
I don’t see why you want
list-style-type: none; text-align:left; float:left;
As these have no use on that menu. Again if you are trying to solve an issue tell us what the issue is.
To change the size, add it in the first part
a {padding:0 7px;font-size: 125%;} %selector% a:hover {text-decoration: underline;}
If you wanted the menu to be on the left use
{float:left;} %selector% a {padding:0 7px;font-size: 125%;} %selector% a:hover {text-decoration: underline;}
So focus on telling us what you want to change from what is there