What should I be studying

@Martin, I was actually looking for a list in priority.  What do you mean "Browser to Server"?

You should be answering questions here.  That will tell you what you do and don't know.

@Dave that is a good idea. I do answer questions at times and should give back more.  I'm just on a learning kick at the moment and am interested in opinions.

Learning is best reason for answering questions.  That's why most of us do it.  People ask questions about things you didn't think of and you have to do research to figure out the answers.  I'm sure you've seen a lot of the demo pages and programs that Ray Paseur and I have posted.

I would say SQL and Node depending on what you think would be the most useful to your future.  I always say knowing some about databases and querying can really help if you are architecting full systems.  If not, then you can do some cool stuff with node.

HTML

CSS
Javascript
JSON
jQuery
AJAX
PHP
MySQL

I recommend that you test how well you know these elements by trying to help others or practice the knowledge in a real-world setting. This will help you quickly identify your weaknesses and allow you to research that subset on-the-fly.

I there a way to setup a notification via email if a question is posted under a certain topic?  I just went through the settings and the only place that really stands out is under skills but nothing that specifically addresses being notified of questions that fall within my knowledge base.  Or do I just need to to go to "Contribute" more frequently?

I find that when I do answer questions I receive a few emails when new questions are posted but they come infrequently.  Can someone explain?

@rgrandlund You can go to this page Contribute on EE to learn more about how find questions/get notified about open questions.
Under the tab "Answer Questions" there is section called "Create Expert Alerts" and it shows step by step on how to set up open question alerts.

I would add .htaccess (*nix) and mod_rewrite (ms) as well as CHMOD/permission knowledge to your list as well to round off your full stack.

You don't necessarily have to learn new languages.

Personally after learning basic web development languages I decided to learn more about devops sort of things. Servers, hosting, cloud, apache, routers, load balancers, domains, cdn, serverless, VM / hypervisors / containers, permissions & security, hardware resource estimation, resource pooling, etc.

You can also learn to do new things with your existing languages. Mobile app development, mixed reality AR / VR, wearables, artificial intelligence, etc.

greetings  rgranlund , ,   I tend to agree with what  Brandon Lyon  said as - "You don't necessarily have to learn new languages", and at one time, I sort of made the mistake of trying to learn "Extra" languages, platforms, and this only wasted my TIME on some things that I never or rarely used for profit or fun.

The Web Pages now are designed for the phone browser market, and require knowledge of HOW and WHY the  many sections of code. on page-( HTML, CSS, Javascript) and on sever-( PHP, SQL) and interaction AJAX, all Work Together to make a user Interactive web site (sort of the "Full Stack" attitude), , , ,  , Pages with ajax implemented page section changes, from user touch tabs or selects or icons, instead of many different separate web pages of different products, articles, blog posts.

So I would say to improve your Web Page develoment skills you might look up top sites  or award winners in Web Page Development and presentation to see what is possible for your sites, and then try and see what techniques and operations are used on the pages that you consider to be a good presentation of Interactive results. There's plenty you can learn about page building by learning more about the things you already have studied, with out using your time to learn a new platform? Just my opinion.

I concur with Brandon.  After you've learned so many languages, learning others to a reasonable functional level isn't too hard (learning to expert level where you understand the intricacies of the language takes many years of course).

However, the number 1 thing I find lacking for many developers/engineers is the 3rd dimension of the "full stack"; servers, deployment, uptime, proper development life cycle, etc.  Many will term it devops or agile.  Some give it fancy titles like SRE.  Doesn't matter.  It's about understanding requirements, and doing things in such a way to deliver results fast and minimize/eliminate any potential impact to your users (100% uptime while improving the service).  

For example, you have 2 engineers.  One is God's gift to JS.  The other is mediocre but gets the job done but not as elegantly, dynamically, or efficiently.  The former writes code that is hard to understand by "mere mortals", has little/no test suite, monolithic design and has issues with every deployment.  The latter does small iterative, micro-service designs with lots of tests and rarely if ever has issues when deploying or even down time (because they realize their code isn't the best and wants to allow a rip/replace methodology).  Which do you think customers will like more?  This is the way, at least, big companies are moving.  Trust me, users won't care that the solution takes 2x longer.  They will trust the solution better because things aren't always breaking.

just my 2cents anyway

@Martin Miller,

Why is the author's comment  (https://www.experts-exchange.com/questions/29090374/What-should-I-be-studying.html?anchorAnswerId=42507129#a42507129) assigned 500 points - the comment is essentially asking a question not providing a solution?

Since this is a great question, let's give all the points to the OP's #a42507129 (list of their full-stack knowledge as a placeholder); otherwise, the split would be subjective and minuscule (100 pts to each of the ten contributors, selecting Slick812 as best solution for the most thumbs up?).

Can we close this question?

Just note popularity on the survey are...  just numbers:-)   There is significant demand in rarer skills, e.g GO for DevOps.