Comment Re:Sandbox (Score 1) 137
The sandbox adds security restrictions plus "tokens" for explicitly allowing the things that you, the site developer, want. The main purpose of the restrictions is to prevent content within an iframe from accessing content in or related to the parent page. For example, lots of ads are loaded in iframes, the sandbox attribute can prevent JavaScript in the ad from executing. The site Can I Use is a decent place to look for which browsers and browser versions support particular parts of HTML5, CSS3, etc. The iframe sandbox has had support from Google and Apple but Microsoft only added it in IE10 and no version of Opera on any platform has it.