I upgraded Safari to version 6 on OS X Lion 10.7.4
The browser is really fast but with one problem, it keeps suddenly crashing and closing. Relaunching it wont prompt with the usual suspects: "Ignore" and "Report to Apple".
A common reason for an application crash is a corrupt preference file. The first thing you'll want to try is backing up and deleting your preference file for Safari.
Close Safari, and then you can find the preference file by going to
~/Library/Preferences and looking for the file called
com.apple.Safari.plist. Once you've found the file, back it up by adding a tilde to the front of the file name so it becomes
~com.apple.Safari.plist. Once you restart Safari, it will generate a new .plist file.
If that doesn't work, the next step would be to do a permissions repair using Disk Utility, which you can find in
Disappearance of Safari without a crash
The browser may disappear without crashing.
First, for the time of the disappearance, seek a matching
.crash file for
WebProcess… at the following path:
.crash file around the time of the disappearance, then use Console to see whether the following line was logged a second or two before the disappearance:
Received an invalid message from the web process with message ID 323002f
If you're using a proxy: this might be related to proxy settings in combination with WebSockets, as also noticed on Meta Stack Overflow. Though there it was reported for Mountain Lion, and it did show the option to send a crash report, and hence find some more details. Still then, maybe the symptoms are the same?
The blog post Networking Crashes In Mountain Lion and its comments blame crashes that refer to "CoreSchedulingSet::copyWithUpdatesReleaseSelf" to either the "Auto Proxy Discovery" and "Automatic Proxy Configuration" settings, or a VPN connection.
Some more investigation on 10.8, with only "Auto Proxy Discovery" enabled, without restarting Safari:
Safari 6 often crashes for Stack Overflow, but only when logged in. Super User crashes much less often, but also shows the issue. When not logged in, all is fine.
Going to websocketstest.com often (but not always) crashes Safari right away.
Going to the Echo Test on websocket.org seems less troublesome. Repeatedly connecting and disconnecting might not cause trouble, but it too will crash at some point.