HTML + CSS: Ordered List without the Period?

This is perfectly possible to do with just CSS (2.1):

ol.custom {
  list-style-type: none;
  margin-left: 0;
}

ol.custom > li {
  counter-increment: customlistcounter;
}

ol.custom > li:before {
  content: counter(customlistcounter) " ";
  font-weight: bold;
  float: left;
  width: 3em;
}

ol.custom:first-child {
  counter-reset: customlistcounter;
}

Keep in mind that this solution relies on the :before pseudo-selector, so some older browsers — IE6 and IE7 in particular — won’t render the generated numbers. For those browsers, you’ll want to add an extra CSS rule that targets just them to use the normal list-style:

ol.custom {
  *list-style-type: decimal; /* targets IE6 and IE7 only */
}