There's probably something else wrong, but allowing division by zero seems like a bad idea and will crash mozilla on Linux/Alpha without this patch. If you want to assert that it's not zero you should state it explicitly..i.e. assert(springConstantsRemaining != 0). Index: nsBoxFrame.cpp =================================================================== RCS file: /cvsroot/mozilla/layout/xul/base/src/nsBoxFrame.cpp,v retrieving revision 1.24 diff -r1.24 nsBoxFrame.cpp 924,925c924,927 < < float stretchFactor = sizeRemaining/springConstantsRemaining; --- > > float stretchFactor = 1; > if(springConstantsRemaining) > stretchFactor = sizeRemaining/springConstantsRemaining;

This has been fixed. Divide by zero should not happen.

Based on the comment's below, marking as verified fixed.