The NoScript extension can be added to point out potentially hostile JS scripts. Safe email processing (avoid all URLs) and browsing only at trusted sites and will also help. The ZDNET article also notes that this could be a fairly complicated and lengthy fix.
0day vulnerabilities in Firefox, with source
This quote describes why no browser can be considered completely safe:
Hackers claim zero-day flaw in Firefox
Snyder said she isn't happy with the disclosure and release of an apparent exploit during the presentation. "It looks like they had enough information in their slide for an attacker to reproduce it," she said. "I think it is unfortunate because it puts users at risk, but that seems to be their goal."