Extra space on the sides of the Webpage..

Hello,

This is going to be a tough one for people to answer as the site in question is hosted locally as it is in development. However I hosted it briefly using SiteGround and the person I was developing the site for noticed that there was extra space on the sides when viewed on a PC. This wasn’t the case when I viewed the site on a Mac or when my friend looked at the site on an IPad or using a mobile phone.

Is this a common issue – I understand that it might be difficult to diagnose but if there is an obvious answer please could someone help??

Many thanks

Nick