In an HTML document, CSS class selectors match an element based on the contents of the element's class attribute. The class attribute is defined as a space-separated list of items, and one of those items must match exactly the class name given in the selector.
In Mozilla applications like Firefox, the -moz-outline-radius CSS property can be used to give outlines rounded corners. An outline is a line that is drawn around elements, outside the border edge, to make the element stand out.
A CSS pseudo-class is a keyword added to selectors that specifies a special state of the element to be selected. For example :hover will apply a style when the user hovers over the element specified by the selector.
A formal grammar, the CSS value definition syntax, is used for defining the set of valid values for a CSS property or function. In addition to this syntax, the set of valid values can be further restricted by semantic constraints (like, for a number to be strictly positive).
The ::-moz-progress-barCSSpseudo-element applies to the area of an HTML <progress> element that represents the amount of progress that has happened so far. This lets you, for example, change the color of progress bars.