The revert CSS keyword rolls back the cascade so that the property takes on the value it would have had if there were no styles in the current style origin (author, user, or user-agent). In author stylesheets (the normal case), for the purposes of the given declaration, it's as if there were no author-level styles, thus resetting the property to the default value established by the user-agent stylesheet (or by user styles, if any exist).
The <string>CSS data type represents a string. It is formed by a Unicode characters delimited by either double (") or single (') quotes. A double quoted string cannot contain double quotes unless escaped using a backslash (\). The same practice applies for single quoted strings, they cannot contain single quotes unless escaped using a backslash (\). The backslash character must be escaped to be part of the string.
The text-decoration-style CSS property defines the style of the lines specified by text-decoration-line. The style applies to all lines, there is no way to define different style for each of the line defined by text-decoration-line.
The text-indent property specifies the amount of indentation (empty space) should be left before lines of text in a block. By default, this controls the indentation of only the first formatted line of the block, but the hanging and each-line keywords can be used to change this behavior.
::before creates a pseudo-element that is the first child of the element matched. It is often used to add cosmetic content to an element by using the content property. This element is inline by default.
The ::first-lineCSSpseudo-element applies styles only to the first line of an element. The amount of the text on the first line depends of numerous factors, like the width of the element, width of the document, and the font size of the text. As all pseudo-elements, ::first-line does not match any real HTML element.
The :hover CSS pseudo-class matches when the user designates an element with a pointing device, but does not necessarily activate it. This style may be overridden by any other link-related pseudo-classes, that is :link, :visited, and :active, appearing in subsequent rules. In order to style appropriately links, you need to put the :hover rule after the :link and :visited rules but before the :active one, as defined by the LVHA-order: :link — :visited — :hover — :active.
The :invalid CSS pseudo-class represents any <input> or <form> element whose content fails to validate according to the input's type setting. This allows you to easily have invalid fields adopt an appearance that helps the user identify and correct errors.
The :link CSS pseudo-class lets you select links inside elements. This will select any link which has not yet been visited, even those already styled using selector with other link-related pseudo-classes like :hover, :active or :visited. In order to appropriately style links, you need to put the :link rule before the other ones, as defined by the LVHA-order: :link — :visited — :hover — :active. The :focus pseudo-class is usually placed right before or right after :hover, depending on the expected effect.
The negation CSS pseudo-class, :not(X), is a functional notation taking a simple selector X as an argument. It matches an element that is not represented by the argument. X must not contain another negation selector.
The :only-child CSS pseudo-class represents any element which is the only child of its parent. This is the same as :first-child:last-child or :nth-child(1):nth-last-child(1), but with a lower specificity.
The :optional CSS pseudo-class represents any <input> or <textarea> element that does not have the required attribute set on it. This allows forms to easily indicate optional fields, and to style them accordingly.
The :out-of-range CSS pseudo-class matches when an element has its value attribute outside the specified range limitations for this element. It allows the page to give a feedback that the value currently defined using the element is outside the range limits. A value can be outside of a range if it is either smaller or larger than maximum and minimum set values.