Update: What I have tried to do is take the version of the browser which is closest to a release version.In case of firefox, the nightly versions eventually become the release version. And in case of chrome for mac, the daily builds are the only ones available [dev channel is also forked from the daily build]. Since I'm not sure whether webkit changes will appear in Safari, I have chosen Safari Beta instead of Webkit. The Safari Beta is the latest beta offered y Apple (5528.17). If someone can confirm whether webkit changes will end up in Safari, I will be happy to include the webkit scores too.