Webmaster Forum / HTML, CSS, Scripts / CSS / August 2008

Because a style set directly on an element has higher specificity than
stylesheet rules that match the element (in other words, the
directly-set style takes priority over the ".demo td" selector in the
inline stylesheet), while the ".demo td" selector has greater
specificity than the ".test" selector, the former consisting of a class
selector compounded with an element selector, while the latter consists
of only a class selector. See

http://www.w3.org/TR/CSS21/cascade.html#cascade

for details. From there, you will see that the style attribute has
specificity 1,0,0,0, the ".demo td" selector has specificity 0,0,1,1,
and the ".test" selector has specificity 0,0,1,0.