Using "ul" list within a table

The following cold works for displaying all items on a single row. But,
it stops working if I put the same code with ul#menu {} and ul#menu li {} in Style.css, and use <ul id=”menu”> … .

Could anyone help me? Thanks.

ul {
display: inline;
margin: 0;
padding: 0;
}
li {
display: inline;
padding: 0 0.5em;
border-left: 1px solid #000;
}