I am 3-4 weeks old to WordPress, so it is possible if I stick around long enough I will learn that the bug I am about to suggest may be old news. Anyway....
..When I edit my blog in Safari, my editing pages for creating new entries and editing old ones is very basic. Compared to my experiences of doing the same tasks in Opera and Firefox, using Safari might be considered the boring way to go. In Opera and FF, you have these great tool bars above the editing areas, and it is WYSIWYG. However, I prefer Safari for the simple reason that it appears FF and Opera (which make use of WYSIWYG) add <P> tags and closing </P> tags where they do not belong, so you end up with pages with one more P tag or not enough closing P tags and then our pages will not validate.
This has happened to me 5-6 times so far. So much so that I no longer edit in anything other than Safari.
Has anyone else run into this?