How do I disable the auto-updating of the Top Sites in Safari? I don't want to turn the feature off altogether, I just want to prevent auto-update. I know this may seem like an attempt to defeat the purpose of Top Sites in the first place, but I find that if it auto-updates any of the Top Sites that are forum-based, all of the unread topics are marked as read. So, an even better solution would be the ability to exclude the auto-update of certain URLs/domains, etc. Does that functionality exist?
I found this somwhere else which may solve your problem:
Open Terminal (Applications/Utilities) & paste:
defaults write com.apple.Safari DebugSnapshotsUpdatePolicy -int 2
then hit return & quit Terminal.
defaults delete com.apple.Safari DebugSnapshotsUpdatePolicy
To disable TopSites, quit Safari, open Terminal and type or paste:
defaults write com.apple.Safari DebugSafari4IncludeTopSites false
Press Return key. Relaunch Safari.
If you use Safari's Private Browsing mode, Top Sites will not update at all. However, this solution might not completely address your original question - I haven't found any solution that could turn-off auto-updates of Top Sites, either completely or selectively for certain URLs/domains.