Menu Links Underlined

I used the following css to underline all links:

a {
text-decoration: underline;
}

but it also underlined my links to my pages in the menu bar of my site. How do I remove that?

I used css link the following to make the menu bold (and I have one that colors it different), but I am trying to make all the links in my widget areas and content areas underlined without the menu being so.

.nav li a{
font-weight : bold;
}

My site is: http://grangerwashington.org/