Face precedence

[Matthew Calhoun <calhounm@mac.com>]

Hello,

I'm trying to figure out what determines the order in which faces are 
applied to a block of text. I have highlight face, which is applied to 
whatever line point is on, defined as white text on a dark background. 
But in programming modes I also have some syntax-related faces defined 
with a light background. Strangely, in some of these modes the 
highlight face's light foreground is applied, but not its dark 
background. Instead, the syntax face's light background is displayed, 
resulting in light text on a light background. What I would like to do 
is make sure that highlight face always takes precedence over whatever 
other faces are applied to the text.

I'm sure this is possible, but I haven't been able to find or figure 
out how. Can anyone point me in the right direction?

Thanks,
Matt