Clever. Having this as an opt-in will help browsers maintain their all-important performance stats.

@Christopher Dean
On which platform/version are you seeing differences between Safari/FF/Chrome?

@sii
The CSS3 Fonts spec contains more explicit controls. I was pushing for kerning to be on by default but Apple *and* MS folks (Sylvain) preferred an 'auto' setting which would the browser to decide, along with explicit on/off settings.

Nice!

text-rendering: optimizeLegibility; = instant site upgrade. Quick, somebody write a Chrome extension that forces this on all sites.

'optimizeLegibility' Safari Extension here:
http://cmorrell.com/misc/optimize-legibility-safari-5-810

I had the following bug in Safari 5: When I have a font with 'cpsp' it's turned on with optimizeLegibility. It shouldn't.

Ah, someone's already made one for Chrome.
https://chrome.google.com/extensions/detail/deglagpfendnbepmjmfmghphlcdl...

@jdaggett

Platform:
MacBook Pro 5,1
Intel Core 2 Duo

Firefox 3.6.6: below

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Safari 5.0: below

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As you can see in the Firefox version, the Ty does not appear kerned in either condition while the ffi ligature appears in both.

In the Safari version, the differences are clear.

I do not have any other browsers on my machine.

Hope this is of some help.

Set up a bugzilla account and file a bug report.

Two things:
I don’t think having an ‘ffi’ ligature by default constitutes a bug.
The sans-serif in your Firefox sample is Verdana, the one for Safari is Helvetica. Verdana does not sport any kerning pairs.