Fill the whole page and keep the contents centered when zooming

I'm facing a problem while making a webpage. I want the contents to be 100% of the browser width and when users zoom out the background should appear. Everything works great as long as the width is set in pixels. This doesn't work if the width is set with percentage. Objects just stay at left/right and drift apart when zoomed out. In what direction should I search to fix this problem? Is this even possible? What other methods should be considered to keep webpage looking kinda good when zooming out/in?

I hope I was clear enough. I'm still new to this. If necessary I will provide code. I wasn't sure about what I should and should not post.

Here is a picture of how I'd like it to look: http://ift.tt/2ij1Lto and here is how it actually looks: http://ift.tt/2hpZ9Wa

Thanks!