Is this similar to what you are trying to accomplish?
I changed the width to 300px for the demo at jsfiddle. Just change 300px
to 900px
HTML
<body>
<div class="width900">
Width of 900px
</div>
<div class="widthfull">
<div class="text">
Width of 100%
</div>
</div>
<div class="width900">
Width of 900px
</div>
</body>
CSS
body {width:100%;}
.width900 {width:300px; background:#ccc; margin:auto;}
.widthfull {width:100%; background:#eee; margin:auto;}
.widthfull .text {width:300px; margin:auto;}
solved My
is bigger than my [closed]