I\'ve noticed a significant difference in rending of Open Sans (Google Web Font) from Chrome, to Safari/Firefox. I attach two photos, the first being chrome and the second s
There is an issue where Safari renders fonts at fixed sizes and other browsers render them more exactly:
example at tech.Ozake.com
So if you request your text to be a size that falls between two of Safari's steps, you will get a different result in Safari than in other browsers.
So depending on how you declare the font sizes and how the window is sized, you will get differently-sized results.