If your pages seem to look wider than your other pages make sure you have resized your photos to make them web ready. Photo's need to be resized to 400 pixels wide for the web. An image resizer will help you get all your photo's web ready.
If you are working in the 4.0 Design Gallery check to see if you have the tool that is marked for the width set to "justified" or setting at 100 %. The normal parameters so the header does not stretch is 750 pixels wide and set to "center".
Also check to see if
photos have been added and they need to be made smaller on the page. A
Word doc. may also been inserted that needed to be "cleaned" before
pasting.