@ngdoc overview
@name Developer Guide: Templates: Working With CSS in Angular
@description


Angular sets these CSS classes. It is up to your application to provide useful styling.

# CSS classes used by angular

* `ng-invalid`, `ng-valid`
  - **Usage:** angular applies this class to an input widget element if that element's input does
    not pass validation. (see {@link api/ng.directive:input input} directive).

* `ng-pristine`, `ng-dirty`
  - **Usage:** angular {@link api/ng.directive:input input} directive applies `ng-pristine` class
    to a new input widget element which did not have user interaction. Once the user interacts with
    the input widget the class is changed to `ng-dirty`.


## Related Topics

* {@link dev_guide.templates Angular Templates}
* {@link forms Angular Forms}