Added a 10px vertical margin between the 2 div in the following 5 reftests:
src/backgrounds/background-color-029-ref.xht
src/backgrounds/background-color-093-ref.xht
src/colors/color-005-ref.xht
src/colors/color-006-ref.xht
src/colors/color-144-ref.xht

Created and added first-letter-selector-028-ref.xht
as a reftest for first-letter-selector-028.xht