Ads can be edited, don't worry about mistakes. During the validity of the ad it can be edited by you frequently, unlike print ads.
Premium ads are graphic ads and positioned in multiple locations of the website including the home page, by rotating all the premium ads daily. Also, there is separate section for all premium ads. Typically the premium ad will be in 3 or 4 places on the website on a given day.
Classified ads are only visible in the classified section.