Ramnimus - the s/z difference is a British/American difference. IIRC it came about when the US 'rationalised' (or 'rationalized') American English in the 19th century. That's when all the -burghs became -burgs too. Bill Bryson tells the story of the development of American English in 'Mother Tongue' - worth reading for entertainment value alone. The 'z' spelling is correct in the USA, the 's' in the UK. Adding to the grammar list, 'of' for 'have'. 'I shouldn't of had that last whisky' is incorrect. 'I shouldn't have had that last whisky' is correct. < /pet peeve > =)