sensible class names for categories

I am guessing this must have asked already but…
my sidebar currently outputs my categories list as below….
Can I set it to just give each li a class of “category” rather than “cat-item cat-item-10”?

Even better could I get it to asign an class of “category-act” if one of the categories is active?

I have looked all over but can’t find a topic which covers this….

code:…..

<ul>
			<li class="cat-item cat-item-20"><a href="http://school.designzest.co.uk/?cat=20" title="View all posts filed under Fund Raising">Fund Raising</a>

</li>
	<li class="cat-item cat-item-10"><a href="http://school.designzest.co.uk/?cat=10" title="View all posts filed under School News">School News</a>
<ul class='children'>
	<li class="cat-item cat-item-6"><a href="http://school.designzest.co.uk/?cat=6" title="View all posts filed under Trips">Trips</a>
</li>
	<li class="cat-item cat-item-7"><a href="http://school.designzest.co.uk/?cat=7" title="View all posts filed under Year 1">Year 1</a>
</li>
	<li class="cat-item cat-item-14"><a href="http://school.designzest.co.uk/?cat=14" title="View all posts filed under Year 2">Year 2</a>
</li>

</ul>