Kelly, I`ve just found out why this happens, Kim had the same problem so I emailed freewebs and asked them. This is how they replied.
Dear FreeWebs User,
Sites are free with no ads (except the Freewebs Freebar at the bottom) for 45 days. After that, an advertising banner about 1 inch tall will automatically appear at the top of each page. Furthermore, we remain committed to maintaining the integrity we have and guarantee that ad content will be appropriate for all audiences.
Premium sites are not affected at all by this and we will never force ads on premium user sites. While many users don’t mind an ad on their site, others prefer not to have it. Premium Services start at under $1 per month, upon which you will receive greater services and features with your account.
Also, we recommend that you periodically view the section for New Policies from time to time in case future changes may effect the use of our services.
Best Regards,
FreeWebs
Hope that helps