After clicking Back button, View Source is greyed out in EDIT menu and absent from right-click menu. To replicate: go to google, do a search, click Back, try to view source.
Confirmed with a local debug build of WebKit r24619 with Safari 3 Public Beta v. 3.0.2 (522.12) on Mac OS X 10.4.10 (8R218). This is a regression from shipping Safari 2.0.4 (419.3) with original WebKit on 10.4.10.
<rdar://problem/5361870>
This is: <rdar://problem/5258776> REGRESSION: View Source Menu is disabled after going back (missing didFinishDocumentLoad callback) which is fixed in TOT Safari (not in WebKit though, that bug is tracked by <rdar://problem/5259339> didFinishDocumentLoad callback is not sent for (some?) cached page loads). Since the fix was in Safari, and not WebKit, it'll be broken in nightly builds until we ship a new version of Safari.
Or, alternately, it will be broken in nightlys until A - a new version of Safari with the workaround ships or B - someone fixes the WebKit end of things.
Marking this as RESOLVED/INVALID because this is a Safari issue, not a WebKit issue. (The bug is otherwise valid, and will be fixed per Comment #3 and Comment #4.) Thanks Justin & Brady!
*** Bug 14850 has been marked as a duplicate of this bug. ***