Character Mis-placement in Firefox

Can anyone tell me why the diacriticals in Hebrew-character fonts, like the ones in this article, are misplaced, when I look at it in Firefox?

If you look at words containing alephs, you'll see that most of them have a little mark underneath the character to its left. The mark should be under the aleph itself. This makes the words hard to read, and is a bit like having the dots on every 'i' appear over the following character.

Background info, not directly relevant.

• The text is in Yiddish, not Hebrew. Yiddish is a Germanic language, like English, but uses the Hebrew alphabet for the same reason we use the Latin alphabet: the people who started writing the language picked an alphabet they already knew. Hebrew-language text has the same problem.
• The diacriticals are under the following character, not the preceding one. Hebrew script, like this, is written right-to-left, not left-to-right.
• The diacriticals change the character -- just like drawing a horizontal line across the top of an 'l' turns it into a 'T'. One of the characters is silent, a second is an 'o', a third is an 'a'.