Perian is a venerable swiss-army knife of codecs for the Mac.Whether trying to play an AVI file or some other rare format from the Beige Days, Perian can often help.It is installed by default by many independent Mac techs.Sadly future development has been discontinued, but the software is still available and compatible with OS X through Lion.
If the website you’re visiting is targeted at PCs or uses AVI clips you may find you can’t hear audio or don’t see video when playing media.
This software is currently being updated for 64-bit Lion and Mountain Lion support, and is available for download via the Telestream website.
The paid Pro version allows for encoding and saving files into Windows Media formats in addition to playback.
Current software (v11 as of this writing) supports Intel-Macs only. The lack of a current Flash player is one of the issues accelerating obsolescence for Power PC Macs The Adobe PDF Viewer is another popular plug-in.
When Adobe Reader is installed on your computer, a PDF Viewer plug-in is included which allows for the display of PDF files inside your web browser.