font problem after you installed SimSun

if you just directly install simsun, most of programs will apply it correctly for chinese display without further configurations. but some won't. the screen effect is pretty weird that some are applied in simsun while some are applied in the old font(vague). what makes it like this? i don't know the accurate answer. but i'm sure that there is a global configuration to which those problematic programs conform, so that they have the same problematic font rendering. thing is not that simple,though. i was only able to make chinese utf-8 pages in firefox to  apply simsun by adding it into serif/sans-serif's  alias list. however, those such as rxvt-unicode and opera interface haven't given in yet. something more about font i am yet to know...