you can do that by writing the style class in your corresponding page
there are lots of CSS property for each class just u need to redife the specific one.
for more about class namd and css property
and for quick investigations - use FireBug for FF or IE dev tools.
Thanks for answers.
I used styleClass attribute in modal panel to overwrite style.
It was premature euphoria:)
The following modal panel doesn't work on IE8.
<rich:modalPanel id="mpXX" styleClass="mpClass" >
Strangely enough, if I remove line "filter:alpha(opacity=50); " modal panel works, but with global styles of course.Any ideas, what may be the reason of that beahviour?