As suggested by Karl Kuehn on OmniWeb-L OmniWeb 4.1b4 seems to have problems with forms and width settings.

should be 20% of window width, yellow background, blue text
should be 200px wide, yellow background, blue text, thin red border, double-size text.
should be 20em wide, yellow background, blue text, margin and padding each of 1em.
should be 20ex wide, yellow background, blue text
should be 400px wide, yellow background, blue text