Is it one word or two?
Take a look at these sentences from the Oxford English Corpus:
✗ Thankyou very much for all your help.
✗ The show has generated alot of media coverage.
✗ We had no idea what the night would have instore for us.
The highlighted words in these sentences reflect a current trend in English which you may have noticed: the joining up of fixed expressions whose components are usually written separately.
None of the spellings given above are acceptable in standard British English: you should still write thank you, a lot, and in store as two words. But the shift from two-word to one-word forms is a well-established process in the language. There are many common English words that started out as two-word phrases, e.g. somebody, everyone, today, or tomorrow. Over time they became fused into the one-word forms we use now.
The tendency to join two-word expressions together seems especially strong in the US. It's standard practice to write underway, anymore, or someday as one word in American English, for example, whereas the two-word forms are still the norm in British English:
|US English||British English|
|Plans for next year's project are already underway.||By October, the work was well under way.|
|I know someday my whole family will be together.||I would love to return to Australia some day.|
|We don't even think about it anymore.||I really don't like him any more.|
There's one notable exception to this: you're much more likely to see the one-word form thankyou in British English rather than in American English. This doesn't make it an acceptable spelling at the moment, though the situation may eventually change.