Designing and developing websites needs a lot of knowledge in browser compatibilities. Knowing a list of most popular browsers is mandatory, so you you can know which browsers you have to do the testing on and make sure everything goes well.

Here is the link I used to monitor the ‘competition of popularity’ of different kinds of browsers: http://www.w3schools.com/browsers/browsers_stats.asp

Creating a website that can work flawlessly on every type of browser is very hard (sometimes impossible), but make sure it works on major browsers and at least 90% of overall browsers available.