I'm running into a few issues on my Emacs + Org mode + Python setup. I thought I'd put this out there to see if the community had any suggestions.
Virtualenv:
I'm trying to execute a python script within a SRC block using a virtual environment instead of my system's python implementation. I have a number of libraries in this virtual environment that I don't have on my system's python (e.g. Matplotlib). Now, I set python-shell-virtualenv-path to my virtualenv's root directory. When I run M-x run-python the shell runs from my virtual environment. That is, I can import Matplotlib with no problems. But when I import Matplotlib within a SRC block I get an import error. 

How can I have it so the SRC block uses the python in my virtual
environment and not my system's python? 
Is there any way I can set
    the path to a given virtual environment automatically when I load an
    org file?

HTML5 Export:
I'm trying to export my org-files in 'html5', as opposed to the default 'xhtml-strict'. The manual says to set org-html-html5-fancy to t. I tried searching for org-html-html5-fancy in M-x org-customize but I couldn't find it. I tried adding (setq org-html-html5-fancy t) to my init.el, but nothing happened. I'm not at all proficient in emacs-lisp so my syntax may be wrong. The manual also says I can set html5-fancy in an options line. I'm not really sure how to do this. I tried #+OPTIONS html5-fancy: t but it didn't do anything.

How can I export to 'html5' instead of 'xhtml-strict' in org version
7.9.3f and Emacs version 24.3.1?
Is there any way I can view and customize the back-end that parses
the org file to produce the html?

I appreciate any help you can offer.
Reads like a bug, please consider reporting it at emacs-orgmode@gnu.org
As a workaround try setting the virtualenv at the Python-side, i.e. give PYTHONPATH as argument.
Alternatively, mark the source-block as region and execute it the common way, surpassing org
Run python from virtualenv in org file & HTML5 export in org v.7.9.3