A wise (wo)man once said...
Life is too short to test this in all known browsers.
Make it work, then make it beautiful, then if you really, really have to, make it fast.
Nine people can't make a baby in a month.
Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.
Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.
Microsoft is not the answer. Microsoft is the question. "No" is the answer.
There are 6 times more certified Scrum masters than certified Scrum developers. It seems 6 Scrum Masters are needed to manage one Scrum developer.