[Theme: twenty sixteen] space at bottom and top of page

Hello, Sorry if I have posted this in wrong place.
I just don’t understand if its need to go in some twenty-sixteen thread, and if so how ?

I have read the posted articles and replies and nothing is a solution for me.
I cannot get rid of the small margin at the top and bottom of my page (in yellow on a desktop). Test site is http://www.purrfect-cat.com (just an old domain).
I’ve just been using a temp solution, to set background on admin panel to the surround color, but I would like to control the template, instead of it controlling me.

On a 7 inch tab (ie. samsung galaxy tab lite, portrait) the yellow is gone on top but still remains at bottom
#page {
padding: 0px ;
margin:0px;
} forces the page to 100% width, but the top and bottom never changes.

Thanks,

Neil.