Ad Networks and Exchanges

For most advertisers, however, display ad space is purchased
 via some sort of ad network or exchange. The big three PPC
 ad networks all have space advertising arms; there are also a
number of other large display ad networks that would be glad
 to help you get your ads placed.

the big three PPC ad networks, who aren’t necessarily the big
three display ad networks—although they’re all near the top of
 the list. The advantage of going through these networks is that
 you’re likely to have a prior relationship with them, and it’s
easy to extend from your PPC ads to include display ads to
 the mix.
Here are the networks to start with:

1.DoubleClick by Google
2.Yahoo! Advertising Display Solutions
2.Microsoft Advertising

Most ad networks sell premium space—the exact space you want
 on the sites you specify. But most sites don’t sell out all the
premium space; they still have space available on their sites that
 goes unsold.

Thisremnant inventory is the same exact space as a site’s premium
 space; it’s simply space that is left over after the primary space
 has been claimed. As such, it sells at discount and could be a
good buy for your advertising program.

There are ad networks that specialize in selling remnant inventory.
 These networks buy up the unused space from a variety of
 websites and then package it to their advertisers for pennies
on the dollar. Now, you don’t always get the choice of websites
 for your ad to appear, but you don’t pay as much as you do
with premium space, either.

For the host websites, selling remnant inventory is a lot better
than leaving the available space empty; they get a little bit of
 income, and they don’t have to leave white space on their pages.
 For advertisers, the benefit is purely monetary; you get your ads
 out there for less than you would if you purchased premium space.
To that end, including remnant inventory in your advertising plan might
make sense. Even if you still purchase premium space on the sites you really
want to use, you can supplement these placements with additional remnant
purchases. It’s certainly cost effective.

Display advertising is the best way to establish your brand or
 product online.Most display ads are sold on a CPM basis,
which is fine if you’re most interested in generating impressions.
 There is, however, a movement toward PPC display ads, if in fact
 you have actual conversion in mind.

Display ads can be image-only ads, or they can include all manner of rich
media. State-of-the-art display ads often incorporate Flash animations, video
and audio playback, and even interactive elements for the consumer to click.