Table misalignment on profit/checkout page

Running a very old version of cs-cart though I suspect most of the coding is similar, so hopefully someone can help…please!!! (pulling my hair out on this for months!).

The site table layout is fine (www . sat buyer . co . uk) and when adding a product to the basket, the page it takes you to is fine also, but then if you click 'checkout' to go to the page where you enter all your personal data, the top header moves over to the left to align with the profiles page…I have no idea why and can't see what is forcing it over on that page only (it reverts back on the next checkout page).

Any ideas, really struggling with this one!

Any ideas on this one guys/gals, really struggling to work out what might be wrong.