New Website and Forms not coming over the same

We are updating our website and the Online Express form on the old website looks great, but when it is moved to the new website some of the formatting messes up and buttons appear larger than they used to be. The person updating the website doesn't have access to edit the javascript, they are with an outside company. Would giving them access be the best option or if they have the javascript, they can manipulate with that on the website?
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