If your Safari keeps crashing, or if you are updating Safari (or just have):
Input Managers and other plug-ins from third parties can do as much harm as good. They use a security loophole to reach right into your applications' code and change that code as the application starts up. If you have installed 10.4.11 and Safari is crashing, the very
first thing to do is clear out your InputManagers folders (both in your own Library and in the top-level Library), log out and log back in, and try again.
So, disable all third party add-ons before updating Safari, as they may not have been updated yet for the new version. Add them back one by one. If something goes awry, remove it again and check on the software manufacturer's website for news of an update to match your version of Safari. Remember: Tiger up to 10.4.10 used Safari 2.0.4 or, if you downloaded it, Safari 3.0.3 beta. Safari 10.4.11 uses Safari 3.0.4 which is
not a beta. If Safari 3.0.4 on 10.4.11 is not the fastest browser you have ever used, then something is wrong!
(Trying to revert to Safari 2 when running 10.4.11 can have repercussions, as Safari 3.0.4 uses a completely different webkit on which other applications like iChat, Mail, Dashboard widgets etc also rely.)
Most errors reported here after an update are due to an unrepaired or undetected inherent fault in the system, and/or a third party ad-on. Add-on that have been frequently mentioned here, among others, for causing such problems are Piclens, Saft, AcidSearch and Pithhelmet. If you have them, trash them and go the developer's sites to see if new versions are available for Safari 3.0.4.
You should also ensure, if you are running Tiger 10.4.11, that you have downloaded and installed the correct version for your Mac of Security Update 2008-001.
As Leopard also uses Safari 3.0.4, much of the above may well also apply to Leopard, but is not guaranteed. Moreover:
Some users have mentioned that the latest Flash Player (v.9.0.115.0) conflicts with Safari in Leopard, and that they have needed to revert to v. 9.0.47. This can be downloaded from here:
http://kb.adobe.com/selfservice/viewContent.do?externalId=tn_14266&sliceId=1