HTML and CSS
HTML and CSS are well supported in PyCharm. This section is by no means exhaustive, but does provide a detailed account of the tools that will help you stay productive. PyCharm provides tag completion for HTML, but it has so much more than this that tag completion is the least exciting feature in its feature set.
Emmet
Emmet is essentially shorthand HTML and CSS. You type the abbreviations of what you want, hit Tab, and PyCharm will automatically convert that shorthand into the desired tags and subelements.
For example, if we were to type in div.container, we would be creating a div tag of the container class. In other words, the following:
div.container
turns into:
<div class="container"></div>
with your caret automatically placed inside the div tag.
This section won't teach you the basics of Emmet; the Emmet documentation site does a much better job: http://docs.emmet.io/
However, PyCharm has its own twist on Emmet, and this includes extra support for XML tags as well...