The <custom-ident>CSS data value denotes an arbitrary user-defined string used as an identifier. It is case-sensitive and in each context, several values are excluded to prevent misinterpretations.
The font-kerning CSS property controls the usage of the kerning information; that is, it controls how letters are spaced. The kerning information is stored in the font, and if the font is well-kerned, this feature allows spacing between characters to be very similar, whatever the characters are.
The initial CSS keyword applies the initial value of a property to an element. It is allowed on every CSS property and causes the element for which it is specified to use the initial value of the property.
The <integer>CSS data type denotes an integer number, positive or negative. There isn't any associated unit with the value. An integer consists of one or several decimal digits, 0 to 9, optionally preceded by one single + or - sign.
The <length>CSS data type denotes distance measurements. It is a <number> immediately followed by a length unit (px, em, pc, in, mm, …). Like for any CSS dimension, there is no space between the unit literal and the number. The length unit is optional after the <number>0.
The -moz-appearance CSS property is used in Gecko (Firefox) to display an element using a platform-native styling based on the operating system's theme.
-moz-force-broken-image-icon is an extended CSS property. The value 1 forces a broken image icon even if the image has an alt attribute. When the value 0 is used the image will act as usual and only display the alt attribute.
The -moz-user-modify property determines whether or not the content of an element can be edited by a user. This property is related to the contenteditable attribute. A similar property user-focus was proposed in early drafts of a predecessor of the CSS3 UI specification but was rejected by the working group.
The <percentage>CSS data types represent a percentage value. Many CSS properties can take percentage values, often to define sizes in terms of parent objects. Percentages are formed by a <number> immediately followed by the percentage sign %. Just as is the case with all other units in CSS, there isn't a space between the '%' and the number.
The CSS propertypointer-events allows authors to control under what circumstances (if any) a particular graphic element can become the target of mouse events. When this property is unspecified, the same characteristics of the visiblePainted value apply to SVG content.
The <ratio>CSS data type, used for describing aspect ratios in media queries, denotes the proportion between two unitless values. It is a strictly positive <integer> followed by a slash ('/', Unicode U+002F SOLIDUS) and a second strictly positive <integer>. There may be spaces before and after the solidus.
The <resolution>CSS data types, used in media queries, denotes the density of pixels of an output device, its resolution. It is a <number> immediately followed by a unit of resolution (dpi, dpcm, ...). Like for any CSS dimension, there is no space between the unit literal and the number.