In reply to White spaces:
I do think that letter design which creates good word images (= 'boumas') is very significant in the fovea, and affects readability. Peter confirms the figure of 5-8 letters in the fovea. If the average saccade is around that length, as the wikipedia article says, then this is consistent with much reading being done with the fovea, and only 'skipping' of less important words is enabled by the parafovea, in combination with the brain's understanding of the meaning of the previous text. That's why I said 'semantic'; I doubt that well into the parafovea, where you can't tell 'and' from 'mad', that you get actual meaning.