I have a partially completed website with a very simple custom template in which some of the pages are not accurately left-aligned with the others: i.e. when switching from page to page, in some cases the entire page including the header, horizontal menu, titles and content appears to 'jump' slightly to the left or right in relation to the previous page. In other cases the header and menus correctly remain static when changing pages, so that only the content and titles change.

I assume it's probably a margin or border setting somewhere that I may have changed while setting up the individual pages, but I can't locate the relevant setting(s) or spot any obvious differences between the pages. Can anyone advise, please?

Thanks in advance.