How to open Safari from a WebApp in iOS 7
Solution 1:
Update 10/23/13: Fixed in iOS 7.0.3. Add a target="xxx" attribute to your links to do this. Also works with mailto: and friends.
This is a bug in iOS 7.0, 7.0.1 and 7.0.2 and there's no known way to do this.
It's a regression from earlier versions of iOS, where links that open in Safari work just fine. It appears to be a part of a cluster of problems revolving around opening URLs, with no external URL schemes working (for example "mailto:" doesn't work either).
The usual suspects of working around a problem like this unfortunately don't work (for example using a form and submitting it with a target of "_new").
There's other grave issues, like alert and confirm modal dialogs not working at all.
It may help to submit these as bugs to Apple, http://bugreport.apple.com
Solution 2:
Having an anchor tag with target _blank
will work in iOS 7.0.3 but using window.open will not work and will remain to open within the webview in 7.0.3:
window.open('http://www.google.com/', '_blank');
Solution 3:
This is a known issue for the last couple months of betas. There are no work arounds, and from what I can tell Apple has been silent on any ETAs on fixes, or even recognizing it's a bug. Bug reports have been submitted, but not updated/responded to.
More: http://www.mobilexweb.com/blog/safari-ios7-html5-problems-apis-review