No, it would not effect ordered lists unless you applied it to the ordered list...not recommended since they are 'ordered' to get a symbol of some order-type.
to apply it to an ordered list you would add this to your css:
ol {list-style-type: none;}
although I would have something like:
ol {list-style-type: decimal;}
Have you linked the stylesheet to your html files?? It must be linked to apply the styles. You should see something like the following in your html headers:
Code:
<head>
<title>Some Title</title>
<link href="../Styles/styles.css" type="text/css" rel="stylesheet"/>
</head>
If you haven't linked it, then, using Sigil (Calibre is similar), just highlight all your html files and then right-click on one of them and select 'Link Stylesheets...' then select the css file you want to link.