Should I stay or should I go? (now sing it to yourself)

You should use firefox even if you won't learn html5 and learning basic html wouldn't hurt because you can always use the old html not 5 for websites and will stay that way for a long time.

HTML5 is currently under development. But is definetly the future. Indeed, Internet Explorer 6, 7 & 8 are not compatible. You can check all browsers compatiblity here: http://bit.ly/2aDUGk But, Internet Explorer 9 is already available as beta and is HTML5 compatible.

Which Internet Explorer are you using? From what I know, Internet Explorer 8 and 9 (beta) both render HTML 5 just fine.

I think you're speaking about web development using the new HTML5. I know what you're saying, IE is the most buggy of browsers and incompatible with any standard other that those propietary from Microsoft, but the fact is that most people use it too, so if you're building a web page you should focus on the most wide target you can. Also, you should design your page in a way that it works well with any browser. You must test it with as many of them as you can. Install IE, Opera, Firefox, Chrome, Safari, and others if you can. Why? Because your visitors may have any, and all of them should be able to see it properly. HTML 5 is still too new and many browsers don't support it fully too. Studing it is good, but if you plan to use it right now, I see a good point to better start with the previous standard, which is mostly supported by all.