I built a site using WebEasy offline and uploaded it to Bravenet. Bravenet support tells me there are coding errors causing their footers to appear at the top of the page with the ads.
1- Is there a program that I can use to detect coding errors?

My pages are set to 1024 x 1800 pixels.
2- Could this be the problem?

3- Is there a limit on length of pages on Bravenet? Or as a practical matter is there a length I should limit my pages to?

check your site in html validator

http://validator.w3.org/