All of these are free for you, with a built-in "check for latest version" feature which will do the trick, if you can find it. Alternatively, you can download and reinstall the latest versions to assure that you are up-to-date:
Google Chrome: http://www.google.com/chrome
Apple Safari: http://www.apple.com/safari/download/
These two plug-ins should also be updated. They provide the means for reading PDF files and viewing/hearing multimedia entries.
Adobe Reader (to view PDF files): http://get.adobe.com/reader/
Adobe Flash Video Player (for audio, video and multimedia presentations) http://get.adobe.com/flashplayer/
HAVE FUN and Enjoy!
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