There are two ways in which Safari users can improve how small outline fonts are rendered by their browsers:
1. Finder: System Preferences: Appearance: Turn off text smoothing for font sizes XX and smaller (decrease XX).
2. Safari: Preferences: Advanced: Universal Access: Never use font sizes smaller than YY (increase YY).
You shouldn’t expect visitors to change their default Finder or Safari preferences just to view your website, though. I suggest that you address the problem by doing one of the following:
1. Use a larger font size.
2. Use a bit-mapped font.
3. Use an anti-aliased graphic.
Perhaps some web god will deign you better and more correct advice.