i was wondering how people make a patterned list i.e white then black then white then black etc. how do i do it.

I would think that the easiest way would be to add a class to the <li> tag.

li.black {
     background-color: black;
}

li.white {
     background-color: white;
}

HTML:

<ul>
    <li class="black">This is black</li>
    <li class="white">This is white</li>
</ul>

actually you would only need one class for the 'other' colour (say black) and then make the default list style white when you define the list in your stylesheet

Not in a list
BUT

http://www.candsdesign.co.uk/page-templates/piano-keys/

one day I'll code a cursor that looks like a hand playing the keys

Omg that is horrible (mark-up) chris! Ladynred would shoot you if she saw.

Usually, there's some script involved (PHP, ASP, Javascript) because it's a list generated by the CMS.

Yep

just one of these throw something together as "proof of concept" ideas.

Thanks