Chrome: The Heartbleed bug is among the biggest security vulnerabilities we have seen in recent times. You could manually check sites to see if they have been impacted -- or you could use Chromebleed, an extension that tells you if the site you're on was affected by the bug.
Chromebleed uses Filippo Valsorda's tool to test if the page was hit by Heartbleed and hasn't issued a patch yet. You're going to be safe on the bigger websites like Yahoo, but there's a chance that some smaller operatprs haven't yet patched their servers, so this little protection will help. If you do visit a potentially afflcited site, Chromebleed will pop up a notification warning you, in which case it's best to exit and notify the site's developers to fix the issue.