When creating ad spaces for your ads using the Advertise World Publisher Portal, you may be tempted to create one ad space and use this space in several, if not all locations, throughout your site. This may seem like a good idea at first, but becomes a problem when you wish to examine the performance and effectiveness of each ad space.
It is a far better idea to create many ad spaces for the different areas of your pages. For example, you may wish to create an ad space for your website sidebar, or maybe even go a step further and create an ad space for your home page sidebar. That way, when you measure the effectiveness of the ad, you can actually tell how well the home page sidebar performs against a sidebar ad placed on another page of your site.
Of course, depending on how your website has been built, it may not be possible to have such granular control over the placement of your ad spaces. If you wish to use one ad space in an area that is shared site-wide, such as a website header or footer, then you a free to do so, but it will be difficult to determine which pages are generating most of your ad clicks/leads.