

Visitors get used to seeing a banner and stop clicking on it. So make sure you change your banners often.
Another way of tackling "banner fatigue" is to have multiple banners active at any one time.
Not all visitors will react to a banner in the same way. So make multiple banners and changing the banners will ensure that over time, your banners are attractive to a wide variety of personalities of visitors.
The IslamicBanners.com Banner Exchange Network has the ability to serve different banners for each account.