The 'none' and 'normal' values for the 'content' attribute are ignored. Setting the value of 'content' to the empty string works.
Created attachment 22266 [details]
Example of error
See also bug 13097.
Created attachment 35193 [details]
Another test case
Setting content to empty string does *not* work, and should not.
'content: ""' means to render the element, but with no text inside, so, for example, if there is a padding and a background on the pseudo-element it must be drawn.
'content: none' prevents the p-element from being drawn at all.
Discuss fix at bug 13097