Back in the early days of the Internet, banner ads and pop-ups were all the rage. In fact, companies would spend outlandish amounts of money on these sorts of ads.
Banner ads are still popular, but advertisers are using better judgment in the prices they pay, as well as the creative and marketing messages that they are conveying. Banner placement and size, in particular, is more advanced and well thought out than ever before.
While the trend in the early days was top and side ads, now the 300×250 medium rectangle ad is king. This ad, as seen here from a Google AdWords sample, fits in well with content. At the same time, it is unobtrusive within the content compared to other ad sizes. The price of these banners can be as much as double that of the top banner ads on a web site.
Why? Simply put, readers are more likely to click on these ads since they blend in with the content. Therefore, this is a premium positions that advertisers and those web sites selling advertising covet.
If your web site is advertisement based and you have not implemented these 300×250 ads, it is certainly a good idea to do so.