Repeat Pattern to 100% of the viewport

in CSS i made that code:

   body {
    background-color:#f3f3f3;
    max-width:1920px;
    min-width:1024px;
    margin:0 auto;

but to seperate the header from the content i would like to have a "bar" between them.

so i made:

#zig {
max-width:100%;
background-image:url(../img/zig.png);
background-repeat:repeat-x;
height:25px;

but the Bar doesn't go "unlimited" it just repeat till it reaches "1920px" can i somehow change that? to put

min-width:100%

didn't work

max-width:1920px; /* REMOVE ME */

if you want something to be max-width 1920 than use a container child (of body) element.

what way you #zag DIV will spann the full width of html, body which is dictated by the viewport width.

If #zag is a DIV (and it's not position absolute or fixed) than you need to set only it's height. min-width:100% is not needed since it already spans the full available width - being a block-level element.

html,body{height:100%;}
body{margin:0; font:16px/1 sans-serif;}

header, section, footer{
  display:block;
  margin: 0 auto;
  max-width: 400px;   /* you use 1920. 400 is for demo :) */
  background:#eee;
}

.zag{
  height: 50px;
  background:#0fb;
}

<header>HEADER</header>
<div class="zag">ZAG</div>
<section>SECTION</section>
<div class="zag">ZAG</div>
<footer>FOOTER</footer>