Web browsing and iMac PPC

PPC (PowerPC, PowerMac) indicates you are running a machine from pre-2006.  PowerPCs will always have trouble loading the latest websites, as there is no Silverlight for PowerPC, and you probably need to look at these solutions for Adobe Flash:

https://discussions.apple.com/thread/4781929

PPC means you have a G3, G4, or G5 in Apple menu -> About This Mac.  Intels are not PPC.  The reason I mention that, is this is the iMac PPC forum.  PPC max out at 10.5.8.  Java on 10.5.8 is very limited: https://discussions.apple.com/docs/DOC-6491

If you have an Intel, you at least can upgrade to 10.6.8, which is still limited in terms of Java, but a little better:

https://discussions.apple.com/docs/DOC-5532

If you have at least an Intel Core2Duo or Core i3, i5, or i7, you can upgrade to Mac OS X 10.7.3 or later, but only after checking your software compatibility with this tip:

https://discussions.apple.com/docs/DOC-6271

10.7.3 offers both the latest Java and Flash support to date, and thus will not have trouble browsing any website except the few that require Windows, which can be added through this tip:

https://discussions.apple.com/docs/DOC-2741

Additional web browsing tips are on Apple Support Communities and my own website.