Eric Seidel:
Fill defaults to black, stroke to none. Whether invalid values are ignored or treated as black I don't remember.
Neither! SVG 1.1 defines a “render up until the error” behaviour (which most implementations don’t follow): http://dev.w3.org/SVG/profiles/1.1F2/publish/implnote.html#ErrorProcessing This is not going to change in time for SVG 1.1 Second Edition.
In general the SVG spec is useless in this regard.
http://www.w3.org/TR/SVG/painting.html#FillProperties http://www.w3.org/TR/SVG/painting.html#StrokeProperties
I recommend following what SVG Tiny 1.2 says on this, which is that attributes with unsupported values are ignored: http://www.w3.org/TR/SVGTiny12/implnote.html#UnsupportedProps This is the behaviour that most implementations use, and is what will be kept for SVG 2.0. -- Cameron McCormack ≝ http://mcc.id.au/