This may seem like an inane question, but can I work on the css code of the website - where it shows all of its CSS?
Everytime I try to insert a single line in the “custom css” box, I manage to mess up the entire layout of the website.
For example if I try to make the header fixed on top of the page for all posts, all I manage is to shift it to the left instead of fixing it.
Can anyone help this newb out? 
Or maybe recommend a good css forum or service?
Cheers
Rowan