Ever since support for bidirectional languages was implemented in Mozilla by me and my colleagues at IBM. and through all the improvements and bug-fixes that have been made since, one thing that we never got quite right was text with diacritics, aka nikkud, aka harakat, especially in justified text. This was a real obstacle in the way of my recommending Mozilla or Firefox to my friends, many of whom heavily use sites like Mechon Mamre that feature vocalized Hebrew.
I am happy to say that this is now fixed in trunk builds and the beta of Firefox 3 that will appear RSN. Here are some screenshots of a chapter from Mechon Mamre. Since they are in Hebrew, the “before” shots are on the right, and the “after” shots on the left. Click on the images to see full-size versions.