The problems not in the CSS it in the HTML, you are not closing you List Item tags correctly </li>, and the browser (IE at least) is forgiving you by adding an extra, blank, line.
Code:
<ul type="square">
<li><a href="http://www.Dejerine-Sottas.com/archives/cat_assistive_technology.php">Assistive Technology</a></li>
<li><a href="http://www.Dejerine-Sottas.com/archives/cat_gene_therapy.php">Gene Therapy</a></li>
<li><a href="http://www.Dejerine-Sottas.com/archives/cat_genetics.php">Genetics</a></li>
<li><a href="http://www.Dejerine-Sottas.com/archives/cat_misc_weird_cool.php">Misc. || Weird || Cool</a></li>
<li><a href="http://www.Dejerine-Sottas.com/archives/cat_people.php">People</a></li>
<li><a href="http://www.Dejerine-Sottas.com/archives/cat_stem_cell_research.php">Stem Cell Research</a></li>
</ul>
That should work.
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