Spaces, more or less!
The most common typos in newly submitted manuscripts relate to spaces. When lines are not ‘justified’, words should have a single space between them. Words joined up or spaced too far apart indicate that the author has been careless in editing: not a promising sign.
A manuscript that has not been thoroughly checked should never be sent out. The initial impression created is bad. As an editor, I glance through the story and if I think there might be merit in it, I point out the obvious errors and suggest that the author proofs the text again.
Most writers are willing to cooperate and eventually their books are published.
Of course, the process is slow, as it is seldom that authors find all their own mistakes on their first run-through. There are probably wrongly positioned quotation marks and grammatical errors. If too much reliance has been placed on ‘Word’ spell-check, there could well be words used in the wrong sense. This is where careful editing comes in – and the time it takes to produce the book can take months – or even a year.