since I cannot see your code I can only guess at what is wrong.
The first thing I would do is change li {display:inline} to li {float:left}
The spaces sound like a margin or padding issue. put in this line of code
li {padding:0; margin:0;}
if that fixes the gaps you know now that the gaps came from either padding or margin. play around with it til you figure out where it is coming from.
If you leave that code in your CSS file it will reset the padding and margin of ever li element on your page.
If you can link to the page with the issue or post your code I can help you more.