[eli]

99 percent of what? Browsers ever made? Visitors to your site?

I read that Microsoft added the StartCom CA to Windows in 2009. So I would assume that people browsing the web with ancient, unpatched versions of IE will have problems. How big a deal that is probably depends on your site.

[leej]

i'm assuming you're not joking. it's "browser recognition" and this value is generally 99.9% for paid providers.