Do web developers who are good at their jobs have all the available HTML(5), JavaScript, CSS tags/elements and attributes memorized?

Simple answer is No. But once you're able to use something (whether tag, attribute, function, etc), the idea stays on your head and you'll be able to recall it once you need it again. Some of them you'll be using a lot when working which makes them really hard to forget. LOL! Don't worry, no one knows everything. I believe even the creators of jQuery still refer to http://api.jquery.com from time to time.

Nobody expects you to remember all tags and all css properties, you just have to be able to ask right question and know where to look. MDN (Mozilla Developer Network) is a great place for docs like css properties and javascript api. Stack Overflow is also great for particular issues. Also I recommend css-tricks which runs by Chris Coyler, there you find explanation and demonstration for basically every css issue.  However, all basic stuff after some practice gets remembered for granted: color, borders, sizes, positions, box-shadows, approriate tags and alas. Just code for awhile, and you'll get it.

I am developing websites and web applications from past 3 years now. And when you start developing at first, you will come across new stuff that you will have to memorize to get good with. But as time passes and you come across new projects you get the hang of it,  you remember stuff pretty well but still, when you have to do a specific task which you can't you'll have to lookup how people with same difficulties have solved it. But for now these things will help you the most: http://justbuildwebsites.com/ http://www.css-tricks.com https://www.developer.mozilla.org - MDN reference http://caniuse.com http://www.stackoverflow.com

I use auto-completion for almost everything. I just need to remember 3 first letters of the thing I want use. Sublime Text can work with any programming language. There is always documentation, I  try not to use libs that are not well documented. Usually is better to read documentation before doing something, at least scan through and build index in memory. Opera 12 is my bookmark manager. I have few hundreds of well sorted websites bookmarked by category. It is very usefully collection. At the beginning I was using stack overflow for everything but nowadays I don't rely on it much less anymore. Having just solution is not always the best approach. http://overapi.com/  this is useful, but It will not teach on how to use stuff correctly. Only by making a lot of mistakes and reflecting upon them will give you this understanding.

Google queries will be able to answer most of your problems; it's just a matter of writing the right question. Stackoverflow will supply excellent solutions to most of the problems, you might encounter.

All find it difficult in learning stage. Once you code enough you will get hold of the tags and all. For me , Google and Stack Overflow are only friends. :P Good luck being a web dev!! :)

Try http://Dochub.io I've been using this for years and it's been great. Recently though it seems to be a bit dicey in Firefox. It'll tell you most things you need to know though.

You dont have to learn it by heart like you learn poems (at least I didn't do it), but You have to know, that, for an instance, javascript has such function or class. You don't have to know exact function name, number of parameters or parameters order - we have google, he can memorize this things for us.

Memorized? No. But after you've bumped into the same attributes and classes over and over again, it sticks in your brain. Repetition is the best (at least for me) of learning about the different components of a Web site.   As for a source of reference, W3Schools is good but I find just a list of the attributes to not be great if you're trying to figure out how best to solve a particular problem. That's where stackoverflow really shines. If you can phrase your problem in the appropriate terms, frequently there is a ready made solution to be found.