Well worth spending an hour on this. Gives a good overview of all the features in the Chrome Developer Tools. Along with making use of the PageSpeed Plugin to assist in optimising the delivery of web content.

If you are developing for the web. You will need to know HTML, CSS and Javascript as a minimum. Depending on what web server and software you are running, you will need to be familiar with several other languages. This page ==> http://www.whoishostingthis.com/blog/2014/09/04/learn-to-code/ gives a nice overview of different coding languages, their uses, and potential salaries (in USD) if you are thinking of pursuing a career as a coder.