Banner ads have seen much better days and the introduction of rich media such as Flash has done little to prop up this outmoded form of advertising. Also, software is being released that strips out banner ads, so more users are avoiding advertising entirely.
Banner ads come in three main varieties:
Pay per impression: these ads are generally sold in bundles of 1000, and advertisers pay for each time the ad appears on the site (known as an "impression") regardless of whether visitors click on the ad. Click-through rates (the percentage of visitors who click on an ad) are declining from 3 to 5 per cent a few years ago to less than 1 per cent now, and payments have also headed lower. This has prompted many advertisers to switch to paying only when someone clicks on the ad.
Click-throughs or "pay per action": many advertisers now want a guarantee that they are getting traffic to their site, so most banner programs have become "action based". There is little or no payment for displaying the ad - but the site is paid if someone clicks on it.
Banner exchange programs: while still used, low click-through rates and patchy ad quality makes this program unattractive. At an optimistic 1 per cent click-through, and a ratio of displaying two on your site and getting one displayed elsewhere, 2000 ad impressions bring just 10 people to your site - and you still haven't made a cent. However, the same 2000 ads can be worth around $US2-4 as paid advertising.
Since most impression-based advertising requires 1 million impressions a month to join (see www.doubleclick.com), for small to medium sites the only realistic option is to use a click-through scheme. There are many companies offering this service, but stick to those with a good reputation. Beware programs that advertise above US25c per click-through: they tend to be fly-by-night and you'll rarely see the money. Programs offering US5-20c are the most common, with the lower end accepting sites having under 10,000 visitors a month and the higher end for sites attracting 20,000 and up.
TeknoSurf (www.teknosurf.com): pays up to US20c per click-through and occasionally mixes in impression-based advertising. It has a reputation as a reliable payer (min $US25) and has good reporting, but you need around 10,000 visitors per month.eAds (www.eads.com): accepts lower volume sites and pays US10c per click-through. Very reliable payments - the cheques from the US are sent on the 20th of the month and they arrive in my mailbox in Australia around the 27th.
Some of the banner programs have adult categories but this advertising is a minefield, particularly under new Australian Internet laws and the conditions imposed by many ISPs.