When you click a direct iTunes link in a browser, Apple has traditionally opened the music app automatically or asked you to download it at a blank landing page. That landing is now more soft and helpful, though missing song previews.
iTunes Preview, as it's known, drops browsers at a page with artist, track and album information, along with track pricing, length, ratings and customer reviews. Better still, it now doesn't just hijack your iTunes copy and open it, but offers an "I Have iTunes" link, along with individual "View in iTunes" links for song previews.
It's mostly helpful to those looking to browse iTunes' music catalogue and price out what's available, but it's also welcome relief to those without iTunes tired of seeing a "Don't have iTunes?" message. It's also a music-only feature, but the clever App Store at AppSpot can look at iPhone apps, music and videos without iTunes installed.