css - What the difference between two double point and one in pseudo-selector -
i bit not understand difference between :before , ::before example. 1 should use?
this differentiate between pseudo-classes (such :hover, :focus, :active) , pseudo-elements (such ::before, ::after, ::first-line).
this introduced part of css3, world wide web consortium (the w3c), because pseudo-elements introduced prior syntactic differentiation browsers support both ::before , :before.
according reference @ mdn (mozilla developer network):
browser | lowest version | support of -------------------+--------------------+------------------ internet explorer | 8.0 | :pseudo-element +--------------------+------------------ | 9.0 | :pseudo-element | | ::pseudo-element -------------------+--------------------+------------------ firefox (gecko) | 1.0 (1.0) | :pseudo-element +--------------------+------------------ | 1.0 (1.5) | :pseudo-element | | ::pseudo-element -------------------+--------------------+------------------ opera | 4.0 | :pseudo-element +--------------------+------------------ | 7.0 | :pseudo-element | | ::pseudo-element -------------------+--------------------+------------------ safari (webkit) | 1.0 (85) | :pseudo-element | | ::pseudo-element -------------------+--------------------+------------------ note, css selectors recommendation:
this
::notation introduced current document in order establish discrimination between pseudo-classes , pseudo-elements.
compatibility existing style sheets, user agents must accept previous one-colon notation pseudo-elements introduced in css levels 1 , 2 (namely,:first-line,:first-letter,:before,:after).
compatibility not allowed new pseudo-elements introduced in specification.
references:
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