Controls the actual Selection operation. This doesn't have any effect on content loaded as chrome, except in textboxes. A similar property 'user-focus' was proposed in early drafts of a predecessor of css3-ui but was rejected by the working group.

[Webplatform](docs.webplatform.org/wiki/css/properties/user-select "Webplatform")
[Mozilla docs](https://developer.mozilla.org/en-US/docs/Web/CSS/user-select "Mozilla")
[Caniuse](http://caniuse.com/#feat=user-select-none "Caniuse")