Hola, pues que estaba yo viendo información del whois de la página en 1and1 y un campo me llamó la atención, decía "Organisation" y yo me quedé o.O y me dije "que raro, ¿se habrán equivocado?", así que me puse a investigar antes de sacar conclusiones y me encontré con algo bien interesante en la wikipedia en inglés.

Greek spellings
 -ise, -ize

American spelling accepts only -ize endings in most cases, such as organize, recognize, and realize. British usage accepts both -ize and the more French-looking -ise (organise, recognise, realise). The -ize spelling is preferred by some authoritative British sources including the Oxford English Dictionary—which lists the -ise form separately, as "a frequent spelling of -IZE...". The OED firmly deprecates usage of "-ise" for words of Greek origin, stating, "[T]he suffix..., whatever the element to which it is added, is in its origin the Gr[eek] -ιζειν, L[atin] -izāre; and, as the pronunciation is also with z, there is no reason why in English the special French spelling in -iser should be followed, in opposition to that which is at once etymological and phonetic."

However in their less academic publications, including Fowler's Modern English Usage, Oxford Dictionaries now give prominence to the -ise suffix over -ize. The main work goes on to say "... some have used the spelling -ise in English, as in French, for all these words, and some prefer -ise in words formed in French or English from Latin elements, retaining -ize for those of Greek composition." Noah Webster rejected -ise for the same reasons. Despite these pronouncements, however, the -ize spelling is now rarely used in the UK in the mass media and newspapers, and is often incorrectly regarded as an Americanism. The Cambridge University Press, equal in authority to the Oxford institution, has long favored -ise.

The ratio between -ise and -ize stands at 3:2 in the British National Corpus. The OED spelling (which can be indicated by the registered IANA language tag en-GB-oed), and thus -ize, is used in many British-based academic publications, such as Nature, the Biochemical Journal and The Times Literary Supplement. In Australia and New Zealand -ise spellings strongly prevail; the Australian Macquarie Dictionary, among other sources, gives the -ise spelling first. The -ise form is preferred in Australian English at a ratio of about 3:1 according to the Macquarie Dictionary. Conversely, Canadian usage is essentially like American. Worldwide, -ize endings prevail in scientific writing and are commonly used by many international organizations. For example, "synthesize" is used in international chemical journals.

The same pattern applies to derivatives and inflections such as colonisation/colonization.

Some verbs ending in -ize or -ise do not derive from Greek -ιζειν, and their endings are therefore not interchangeable; some verbs take the -z- form exclusively, for instance capsize, seize (except in the legal phrase to be seised of/to stand seised to), size and prize (only in the "appraise" sense), whereas others take only -s-: advertise, advise, apprise, arise, chastise, circumcise, incise, excise, comprise, compromise, demise, despise, devise, disguise, exercise, franchise, improvise, merchandise, revise, supervise, surmise, surprise, and televise. Finally, the verb prise (meaning to force or lever) is spelled prize in the US and prise everywhere else, including Canada, although in North American English it is commonly replaced by pry, a back-formation from or alteration of prise.

http://en.wikipedia.org/wiki/American_and_British_English_spelling_differences#-ise.2C_-ize