There is a version of Firefox 4 available for PPC Macs:
TenFourFox 4.0.1 Firefox 4 For PowerPC Browser Released
Version 4.0.1 of TenFour Fox, FloodGap's port of Firefox 4 for Power PC
Macs that supports both Mac oS X 10.4 and 10.5. has been released.
Mozilla.org dropped support for OS 10.5 after Firefox 3.6 and for Power
PC with the fourth beta of Firefox 4.
TenFourFox uses almost all the same code as Firefox 4 and has nearly all
the same features, including faster JavaScript, WebM video, and HTML 5
and CSS 3 support, as well as new and emerging Web features, but with
the code needed to keep your Power Mac functional and fast. Out of beta
and it's ready for action, versiob 4.0.1 is a performance, security and
stability update incorporating Mozilla's Firefox 4.0.1 plus AltiVec acceler
-ation for WebM and browser graphics, and G5 JavaScript acceleration.
For more information, visit:
http://www.floodgap.com/software/tenfourfox/
Source: from http://www.applelinks.com - posted April 25, 2011)
Now for the intersting bit: TenFourFox, like Firefox, does not support most plug-ins. Unless you are prone to headaches (in which case don't) you can read about that here:
http://code.google.com/p/tenfourfox/wiki/PluginsNoLongerSupported
But there is a workaround!
Open TenFourFox and type in the address bar: about:config (no spaces) and click return. This gives you a warning that it might harm the application. Ignore that and click on 'I'll be careful, I promise' and you get the config file that you can edit - with great care.
Look/search (scroll down) for: tenfourfox.plugins.enabled
Set it to true. (Double click it to toggle it)
Now close TenFourFox, open it again, and Flash will now work, as it now uses the plug-ins that Safari has stored.
With SilverLight, Microsoft attempted to create their own version of what a replacement for Flash could be - but not to universal acclaim. You can read more about it here:
http://silverlight.net/
So, if you go to any sites that have been designed for this new Silverlight stuff, you can download the plug-in from here (but make certain that you are downloading SilverLight v.1.0 for OS X (10.4.8 upwards) if you are using a PPC Mac, but even this will not work with Safari 4. Version 2 only works with Intel Macs and does work with Safari 4/5. The solution is to download and install the latest version of Flip4Mac, which now includes a Silverlight component:
http://dynamic.telestream.net/downloads/download-flip4macwmv.htm
But the latest news is that Microsoft will probably abandon Silverlight in favour of HTML5:
http://www.appleinsider.com/articles/10/10/29/apples_ios_pushes_microsoft_to_dia l_down_silverlight_for_html5.html and
http://www.bbc.co.uk/news/technology-11673384