The following conventions are used to outline browser compatibility for each CSS feature:
Y = Yes. The feature is implemented completely per the W3C specification of what that feature is.
N = No. The feature is not implemented.
B = Buggy. The feature is implemented but has unexpected side effects.
P = Partial. The feature is partially implemented.
A = Alternative. The feature is not implemented but an alternative proprietary feature is available that provides the same functionality.
I = Incorrect. The feature is implemented but does not conform to the W3C definition of what that feature provides.
The CSS level that reference material refers to is provided in the CSS column. At the time of this writing, there are four CSS specifications:
CSS Level 1: The reference material provided is outlined in the CSS Level 1 Recommendation made 17 December 1996.
CSS Level 2: The reference material provided is outlined in the W3C CSS Level 2 Recommendation made 12 May 1998.
CSS Level 2.1: The reference material provided is outlined in the W3C CSS Level 2.1 Working Draft made 11 April 2006.
CSS Level 3: The reference material provided refers to a W3C CSS Level 3 Candidate Recommendation (at the time of this writing portions of CSS 3 are still in development; references refer to those parts of CSS 3 in Candidate Recommendation status).