I get something a little like that in a select few email messages, and always from certain senders. In my case, it's because (I think) I have set an overall global font size which adjusts all fonts to a specific size, and often it's bigger than that used by whoever composed the message. I'm using a userContent.css file to do this, and I know this isn't a common practice. So in your case, I'd look at '''[http://kb.mozillazine.org/Menu_differences_in_Windows%2C_Linux%2C_and_Mac Tools|Options]|Display|Formatting''' and when there click the '''Advanced''' button (not the Advanced tab). There is an option in these advanced settings to set a minimum font size, and another to allow messages to choose their own font size. Either or both of these settings might be causing the issue you showed us in your picture.