Since the last update of Safari, I’ve been seeing way too much of this error:

"Webpages are not responding. To visit the selected webpage, all webpages in other tabs and windows must be force reloaded. Do you want to visit this page?"

Once this error shows up, usually several windows will start reloading on their own. The error seems to happen only when I have a lot of tabs and windows open in Safari, but since I almost always do, it’s hard to pin that down as a contributing cause.

Apparently many other people have the same issue, as indicated by the lengthy discussion thread here: “This aspect of Safari 5.1 is really lame!”.

Apple does have a technote that addresses such problems in general, while making no admission of guilt or of a wider problem:

Safari: Unsupported third-party add-ons may cause Safari to unexpectedly quit or have performance issues

They suggest removing (not deleting) any third-party addons (not extensions or plugins) to see if that cures the problem. Then you can put them back in one at a time and test Safari.

Unfortunately, there is no interface to do this. You’ll need to locate the items in one or more of these folders:

  • /Library/Internet Plug-Ins/
  • /Library/Input Methods/
  • /Library/InputManagers/
  • /Library/ScriptingAdditions
  • ~/Library/Internet Plug-Ins/
  • ~/Library/Input Methods/
  • ~/Library/InputManagers/
  • ~/Library/ScriptingAdditions

Despite the recommendation that extensions are not part of the problem I found the occurrences of forced reloading to be reduced when I turned off some extensions.

An article in MacWorld that addresses this issue suggests that the behavior is a side-effect of the new architecture of Safari.