Previously, when linking to a song or album in iTunes your browser would open a blank page and prompt you to open the link with the iTunes application. This was fine if you had the iTunes application installed but annoying if you didn't.
Now when visiting an iTunes link Apple has created a web based iTunes Preview page. Here you can find information on the title such as recent reviews, ratings, and other suggestions.
Of course if you do not have iTunes installed you will be reminded that it must be installed to purchase or listen.
Unfortunately, this preview is currently only available for music; however, its likely that Apple will expand this to other categories such movies or iPhone apps.