解决方法
从这里引述：
CSS @media print issues with background-color;
IF a user has “Print Background
colours and images” turned off in
their print settings,no CSS will
override that,so always account for
that. This is a default setting.Once that is set so it will print
background colours and images,what
you have there will work.It is found in different spots. In
IE9beta it’s found in Print->Page
Options under Paper optionsIn FireFox it’s in Page Setup -> [Format & Options] Tab under Options.
