Header Blank Spot When Zooming Out

When I zoom out, the header image shrinks, sticks to the left edge, and leaves a very unattractive blank band across the top of the right site:

#header-wrap {
	background: url(http://mywebsite.com/wp-content/uploads/2013/12/eb6.png) no-repeat ;
	position: relative;

height: 131px; (e.g. 100px);

    width: 100%;
}

thats the code I used to add and position custom header