How do I create a div tag heading with a underline?

Question

See Wikipedia http://en.wikipedia.org/wiki/Css

If you look at the heading, it says "Cascading Style Sheets", then it has an underline.

How do you do that?

.heading1 {
/* heading with underline */
}

Answer 1

h1 {
  border-bottom: 1px solid gray;
}

Answer 2

Use borders:

.heading1 {
    border-bottom: 1px solid #aaa;
}

And if you're using Firefox, get Firebug which allows you to inspect any element's CSS attributes so you don't have to guess how a certain style is implemented.

Answer 3

If the div is 100% wide the you can put a bottom border

.heading1 {
   border-bottom: 1px solid #000;
   width:100%;
}

As everyone said get firebug, you can also use google chrome's integrated inspector(which is like firebug).