If your dictionary gives two spellings for a word, it's too big. I have a 1976 Merriam-Webster three-volume dictionary that came with my copy of the Encyclopedia Britannica, and it's so frigging huge that it has alternate spellings for every damned word.
We tried to use it for Scrabble verification, but you could pretty much play any seven letters and that word is in there. To use the example that Jason mentioned, it says this on page 1223 (of the H-Z second volume):
judgment or judgementWHAT THE FUCK?
Never spend more than about $5.95 for a dictionary. When the book is too big, they start adding "regional spellings" (just outside of Joliet, south of the prison, on windy days, it's spelled...). How the hell can a "reference book" get away with this? Do they make math textbooks with alternate answers for 2+2?
When I look up the spelling for a word, I want ONE ANSWER. That's what reference books are for.