My iBook G4

..To find 'supported web browser' for Tiger 10.4.11 &/or Leopard 10.5.8 is limited..

A browser for PPC G3/G4/G5 see http://www.floodgap.com/software/tenfourfox/

Worth trying. But note: the new internet is slow on older hardware. Also TenFourFox

does not use Flash. For details see their site for build model versions, and more info.

The reason is probably that the web browser is old. You may want to try another web browser, but the choice is limited due to the fact that the Mac OS X versions compatible with an iBook G4 are old as well. A browser called TenFourFox has been mentioned by some.