If you are looking for a solution that works in IE as well, you could float the list elements to the left. However, this will result in a list that snakes around, like this:
item 1 | item 2 | item 3
item 4 | item 5
Instead of neat columns, like:
item 1 | item 4
item 2 |
item 3 |
The code to do that would be:
ul li {
width:10em;
float:left;
}
You could add a border-bottom to the lis to make the flow of the items from left to right more apparent.