How can I make fonts render the same way across different web browsers?

You're not going to get fonts, and some other things, to render identically across browsers. The handling of fonts is a perfect example. I know Safari on Windows likes to make text bold for some reason. Unfortunately this is how the web works. The variety of browsers, OSes, monitors, graphic processors, etc, out there means there's potentially thousands or tens of thousands of different ways a person can view a web page. So when building for the wbe you have to do it knowing and expecting that your site will not be pixel perfect for everybody. This isn't print. It's the wild wild web.