jupyter custom.css removal
Reposting as an answer:
When your changes don't seem to be taking effect in an HTML interface, browser caching is often a culprit. The browser saves time by not asking for files again. You can:

Try force-refreshing with Ctrl-F5. It may get some things from the cache anyway, though sometimes mashing it several times is effective.
Use a different browser profile, or private browsing mode, to load the page.
There may be a setting to disable caching under developer options. I think Chrome has this. May only apply while developer tools are open.
If all else fails, load the page using a different browser. If it still doesn't change, it's likely the problem is not (just) browser caching.
By mistake, I updated this file to customize css.
D:\Continuum\Anaconda2\Lib\site-packages\notebook\static\custom\custom.css
To rollback the above change, 
1) I put back the original file that I saved before. still the new css shows up in jupyter.
2) I removed all .ipython and .jupyter dir and it didn't work either.
3) I even uninstalled anaconda and still that css shows up.
I'm really stuck here. Does anyone know how to go back to the default css of jupyter ?