Safari won't quit

I have experienced this problem, along with: Safari runs at 100% of CPU (check Activity Monitor in Utilities folder) even when not active, causing the fan to run virtually non-stop; Safari browsing history does not work properly anymore. All of these issues appear to be related.

I have tried every suggested fix, but the only one that worked was: with Safari not running, remove the entire contents of ~/Library/Safari, save them to a temporary folder on the desktop, and then re-start Safari. Check Activity Monitor to confirm that Safari is no longer running at near 100% of CPU. Check to see if Safari quits normally. Check to see if the History function is working properly again. Assuming all are true, then something that was in ~/Library/Safari was the cause of all three problems. Since doing that, I have returned the following files to the new Safari folder from the one on my desktop: Bookmarks.plist, Extensions folder, Downloads.plist, and the Databases folder. Everything continues to operate normally. I suspect it may be the History files that caused all the trouble.

shutting down your mac by holding down the power button is ok. AppleCare has instructed me to do this before and they said it would cause no ill effects. Here are many methods to force quit: http://support.apple.com/kb/ht3411

Had similar problem. Tried to fix it by reinstalled the os, worked ok until I installed the Safari 10.0.3 update. Your fix done the trick, simple but effective. Thanks