Reducing white space between content and bottom of page

Hi there

I’m using Everest but I can’t give you the url as the website is yet to go live.

I would like to know how to remove the white spacing between the content and the end of the page. I found the following code on a forum and this has reduced it by a cm but would like another 2-3cm taken off.

.site .hentry {
padding-bottom: 0px;
}
}

Also, there is a grey box around the entire website, can this be removed?

Many thanks!

Hannah