html, css, javascript, these 3 are core, should know these 3 atleast.

Annnddd this is exactly why I think freeCodeCamp needs to restructure their "curriculum."

You should be able to answer this question yourself. Here. let's keep it simple:

This is part of the Linux Kernel. It is written in C. Go read some code real quick then come back to this post.

Now, you tell me. Is it a good idea to "learn the Linux Kernel" without learning or before you learn C, when in fact the kernel is written in C? No, that makes absolutely no sense and it's going to damage your learning experience in the long run.

The same applies to Bootstrap and CSS. Bootstrap is a CSS/HTML framework. This means that it is written in CSS. Why on earth would you think you don't need to learn CSS "after" Bootstrap? You should learn it BEFORE Bootstrap.

More importantly than any of that though, is you need to improve your ability to figure this kind of stuff out on your own. This entire question is ridiculous and I'm not saying that to be mean, but I'm saying that because I don't see you having a very fun or rewarding coding career if you can't figure this type of stuff out because the problems get MUCH MUCH harder than this. For example, if you go to en.wikipedia.org/wiki/Bootstrap_(front-end_framew…) you will immediately see that Bootstrap is a HTML/CSS template so you can reason to yourself like this: "Well, if I want to be good at HTML/CSS and have a full understanding of front-end web development, because I want to be a good front-end developer, then I'd like to MASTER HTML,CSS,JavaScript so that I can build amazing, custom-built websites for clients or for my own enjoyment."

You don't think like this: "Ugh... I am developer. Do I really need to learn how this crap really works? What's the least amount of learning/work I can get away with? Should I Bootstrap after CSS?"

That's very bad and it makes you a terrible developer. We can't teach you that, you have to determine that for yourself. The other thing too, your post looks like you put no effort into it. I know this is true rather than you just being new to the language because you correctly spelled some words and then misspelled those same words after. That means you didn't put in effort. Your post makes little sense and is riddled with English syntax errors. Good luck if you plan on coding like that. You will have many treacherous and frustrating times ahead.

Your question is flawed, and utterly huffing backwards.

In order to have bootcrap do anything it wasn't designed to do out of box, you HAVE to learn CSS; but to be brutally frank (You'll find I'm rarely anything but) you should have a command of CSS LONG BEFORE you even THINK about looking at any fat bloated idiotic halfwit mind-numbingly ignorant asshattery that are HTML/CSS frameworks!

Particularly when how it works is the antithesis of why HTML and CSS are separate in the first bloody place, and it makes you write as much if not more code than you'd have written without it if you had a proper command of HTML and CSS in the first bloody place!

Go find a stick, scrape off the bootcrap, and learn to use HTML and CSS properly BEFORE you dive for the bloated framework chazerei. IF you are able to learn those properly, you will quickly find that NONE of the claims about bootcrap bear any resemblance to reality or sanity. It is not easier, or faster, and it sure as HELL doesn't make you more productive. All you'll end up doing is sleazing out two to six times the markup to write as much custom CSS on top of bootcrap as you'd have without it! Or at least, two to six times the markup if you know what semantics are and how to leverage selectors so you aren't mindlessly idiotically throwing classes at EVERYTHING. As Carlin joked, not every ejaculation deserves a name -- to that end not every damned element needs a div around and three classes atop it.

... and anyone out there making the claims that bootstrap in fact does those things, doesn't know enough about HTML, CSS, progressive enhancement, separation of presentation from content, semantic markup, or accessibility guidelines to flap their yap about it!

tl;dr: read the FAQ :)

Just always remember: What will you do when Bootstrap does not provide what you need? What if Bootstrap becomes outdated (like what happened to jQuery)? How will you go on from there? What if people start hating the Bootstrap style and something new and awesome hits the market? Will you go and painstakingly learn the new library? What about small projects? Bootstrap has a lot of features, but what if you only need very very few of them? Will you set up a build system which removes all the clutter? Or will you send everything to your clients, so they have slow load times and you use up their mobile data volume?

Here's my advice: NEVER START BY LEARNING A FRAMEWORK.

You should definitely take a step back and try to leave Bootstrap completely out of your next few projects. Most stuff can easily be done without Bootstrap. I'd even say that if you get to know CSS and good CSS architecture, it will actually be easier to just do stuff without the framework - instead of using it and then stripping stuff out or modifying and extending it to suit you needs. I highly recommend taking a look at normal CSS and learning BEMIT and ITCSS (combine them!), which are not frameworks, but architectures (think OO or FP for programming languages). That way, you will be able to write efficient, maintainable and scalable style code without 3rd party tools.

Learning CSS will give you a better understanding of Bootstrap and other CSS frameworks. I think if you ever plan to modify the default Bootstrap stuff you are going to want to learn CSS. If you don't modify the Bootstrap stuff or just use themes from other people then perhaps you don't need to learn CSS but I think you would still benefit from CSS knowledge.

Besides Bootstrap there are other frameworks like Foundation that you can learn. Each framework may be different, but CSS will always be the same underneath them so if you learn pure CSS it's knowledge you can carry over to other things.

Actually Buddy

there is a lot of difference between designing and developing.

Designing means to meet the requirements .

Developing is to code that design which had meet your requirement .

Bootstrap is actually a framework made entirely on CSS by two dudes in twitter .They made it for many reasons the major one is to acquire responsive view.

CSS by learning it you will acquire the art of making a webpage awesome while Bootstrap will make it responsive against all screens .

So YES learn the CSS .

Cheers ...