Tim Ahrens writing for Smashing Magazine:

Now that we have a great choice of fonts that can be used on websites, it becomes clear that the translation of a design into pixels is not something that happens naturally or consistently. OS makers apply different strategies to render how typefaces are displayed, and these have evolved greatly over time (and still continue to do so). As we now look closer at fonts on screen more than ever before, we realize that the rendering of these glyphs can differ significantly between systems and font formats. What’s more, it has become clear that even well-designed fonts may not look right on Windows if they are missing one crucial added ingredient: hinting.

This article presents the mechanisms of type rendering, how they were developed, and how and why they are applied by the various operating systems and browsers—so that when it comes time to choose a font for your next project, you know what to look out for to ensure the quality of the typography is consistently high.

It’s a great read, even just to understand why identical typefaces on Windows and Mac OS X look different.