Every time I successfully validate a CSS, I notice that the
"Congratulations!" -text is coloured red. This bugs me. Students of
communication and cognition sciences (and indeed almost anyone else too)
can tell you that in many cultures, red is symbolically a negative and/or
warning color. Therefore, the text "Congratulations!" and its color convey
opposite meanings to the reader. The color is interpreted first
(pre-attentively), text afterwards (cognitively). This has the effect of
making the system both slower and less enjoyable to use. I suggest
colouring "Congratulations!" and other similar texts green, for example.