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Travis Duffer
7,074 PointsWhat is the preferred notation for pseudo elements?
I've noticed a few times while watching CSS videos that the notation switches between double colons and single colons. For instance, sometimes the notation ".main-nav:after:" is used, and sometimes the notation ".main-nav::after:" is used. Which is preferred? Is there a difference?
Also, as a bonus question, I believe I have noticed the pseudo-selector "first-child" or "last-child" is sometimes written with a colon instead of a dash, as ".main-nav:first:child:" Is this an alternative syntax or am I getting multiple concepts confused here?
4 Answers
James Finn
7,055 PointsHi, in the CSS 3 spec, single colons means pseudo class, double colons means pseudo element.
I can't say it better than the master, Chris Coyier of Css-Tricks:
"Every browser that supports the double colon (::) CSS3 syntax also supports just the (:) syntax, but IE 8 only supports the single-colon, so for now, it's recommended to just use the single-colon for best browser support. :: is the newer format indented to distinguish pseudo content from pseudo selectors. If you don't need IE 8 support, feel free to use the double-colon." (Source)
Regarding your final question, your syntax (above) is incorrect because pseudo classes or elements do not contain colons, only dashes. Your syntax should read: .main-nav:first-child{}
Dustin Matlock
33,856 PointsHere's a compatibility table on ::selection.
Dustin Matlock
33,856 PointsIt's essentially the same but the level 3 CSS spec adds an extra colon to differentiate between pseudo-elements and pseudo-classes.
You can use either one but older browsers won't recognize ::. It might also be helpful to check out the grammar section on CSS selectors.
Travis Duffer
7,074 PointsOh my gosh I just messed my syntax all up. I wish I could remember which video I thought I saw the "first:child" notation in. I'm pretty sure I saw it but I can't remember where. Perhaps just a typo in the video.
Dustin Matlock
33,856 PointsMost likely it was Basic Structural Pseudo-Classes.
James Finn
7,055 PointsIt is possible to be confused by the fact that you can combine pseudo selectors. For example, a:visited:hover could be used to declare user interaction styles upon any hover of a visited link.
More info about this here
James Barnett
39,199 PointsJames Barnett
39,199 Points>Your syntax should read:.main-nav:first-child:No trailing colon though.