ßeta is correct in that you cannot install plug ins.
However I use my PS3 connected to an HDTV, with a wireless (usb) keyboard with built in mousepad. Linked via a Belkin wireless router to my PC and internet.
No problems looking at about 90% of sites, e.g BBC, Youtube, PCAdvisor etc etc, all display with no problems.
The navigation between screens and around the PS3 interface takes some getting used to but is easy to pick up.
I have read on various forums that there are plans to incorporate some of the plugins, via the regular system updates which are released for the PS3.
The PS3 is a cracking piece of kit. My PC has started gathering dust.