You will want a grid like Foundation or Bootstrap. You will want like:
<div class="row" id="firstBackground">
<!-- Contents... -->
</div>
<div class="row" id="secondBackground">
<!-- Contents... -->
</div>
<div class="row" id="thirdBackground">
<!-- Contents... -->
</div>
<div class="row" id="forthBackground">
<!-- Contents... -->
</div>
I hope it helps.
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