html tag on page zoom

Question

HTML

Good day! Tell me how to correctly write a piece of code in html so that when you change the scale of pages when you press Ctrl + (zoom in) or Ctrl- (zoom out), the header does not crawl to the left relative to the rest of the page.
piece of code
.sci_topbg { background: #496BAB url(image address/5555.gif) left top no-repeat; width: 1856px; height:155px;}

Answer 1

Most likely you need to set the position (if you are positioning with this) like the content.
Or set margin in one unit.

Answer 2

.header{
 width: 250em;
 left: 50%;
 margin-left: -125em;
}

<div class="header">HEADER</div>