iFrame problems in our website

We have multiple child websites which contain an iFrame from a parent website. The issue is in the child website, the iFrame on child doesn't have the same behaviour as the original site, I believe this is due to Javascript conflicts. For example some buttons don't operate correctly, the page format is different to parent/original etc. We need someone to check the sites and fix it permanently so that any future websites which also use an iFrame to the parent site don't have this problem. Immediate start available, if you have read this please include the word 'iread' in your proposal. Expert freelancer required, no timewasters.