Header changes size in Copywriter theme

Scroll down on this site’s front page and the header changes size! I need it to stay as it is when you first land on the page, ie before any scrolling. I have added extra CSS to make margins:

@media only screen and (min-width: 768px) {
body {margin-left: 300px; margin-right: 300px;
}
}

Obviously before I did this the header was full size and stayed the same when scrolling.

Help appreciated! Many Thanks, TA

• This topic was modified 6 years, 4 months ago by Steven Stern (sterndata).

The page I need help with: [log in to see the link]