themes - How can I version the main CSS file? in WordPress

Style.css is required for your WordPress theme. That's where WordPress gets the theme name and meta information for the Appearance > > Themes menu from. That said, you don actually have to use style.css in your theme at all. I know of several readily available themes that don use it, and I only use it in a handful of my custom designs.

In header.php just place the following tag in place of the regular stylesheet link:

<link rel="stylesheet" type="text/css" href="<?php bloginfo('stylesheet_directory'); ?>
/style-1.css" />

This will load your alternative stylesheet as the page's stylesheet and completely ignore the regular style.css .