Part 1-Banner Ads
There are many different types of advertising on the Web but every website owner decide which one is the best for his business. I belive banner ads it's one of the most popular form of web advertising. It's a graphic image or animation that comes in numerous standard sizes:

- 728 x 90 IMU - (Leaderboard)

- 468 x 60 IMU - (Full Banner)

- 234 x 60 IMU - (Half Banner)

- 88 x 31 IMU - (Micro Bar)

- 120 x 90 IMU - (Button 1)

- 120 x 60 IMU - (Button 2)

- 120 x 240 IMU - (Vertical Banner)

- 125 x 125 IMU - (Square Button)

- (Read IAB Ad Unit Guidelines).

Banners must be designed to attract viewer's attention and link them to the web site of the advertiser. The most popular graphic format for banner ads is GIF, but can also be JPG or PNG. For animated banners are used technologies like JavaScript, Silverlight, Java, Shockwave or Flash.

An effective banner design can make the difference between an unsuccessful and successful banner ad campaign. Some quick tips about building a good banner are:

- use a small animation that can attract attention, but not loops endlessly might irritate the visitors.

- use nice colors that can be similar to your website, also try using your logo.

- write a short message that can be representative to your services, try giving users a benefit for clicking on your banner.

It's seems that
The first clickable web ad (which later came to be known by the term "banner ad") was sold by Global Network Navigator (GNN) in 1993 to a law firm. GNN was the first commercially supported web publication and one of the very first web sites ever. (Source: wikipedia)

Most banner ads are sold on a CPM basis or on a CPC basis.
CPM term refers to the cost per thousand impressions ,that is the cost per thousand times your banner ad is shown or circulated. CPC term refers to cost per click, that means advertisers will pay only for actual visitors.