[Aldo_MX]

Your assumption is wrong, IE is usually the last browser I test. In my experience the rendering of Webkit and Gecko have more issues than Trident.

I don't remember every edge-case I have faced since ever, but for example, the following selector used to fail with Webkit browsers, and the response from Apple were "WONTFIX for performance reasons":

.checkbox:checked + .sibling + .second_sibling { display:block; }

Also, in my experience, the sites that look broken in IE11 (ex. Facebook) is because the website author (or the compatibility lists from MS) set an old/faulty document mode via X-UA-Compatible.

I'm not trying to claim that IE is a better browser than Firefox/Chrome, because this is subjective (and personally I prefer Opera), but I'm trying to say that you must not develop a website in Firefox/Chrome assuming they never have faults.

IE is not as broken as people claim, and there are edge cases where IE is right and the other browsers wrong.