The most popular form of web advertising are banner ads. Banner ads can consist of either text, static images (JPEG/PNG/GIF), animation - most commonly in the form of Flash, or interactivity such as video, games or sound to maximise their appeal. These banner adverts are slotted into a web page with the intention of enticing people into clicking on them, taking the user through to the advertisers page, thus increasing traffic to that site. Internet banner advertising has exactly the same premise as more traditional methods of advertising - It creates greater awareness of whatever the advertiser has to offer its potential customers, and why they should choose them over their competitors.
(aka Leaderboards, Skyscrapers, Banners and buttons/tiles)
Because of the layout of most web pages, banner ads are usually proportioned so that they can either fit along the top of the page, or down the side of the page content, so that they don't interfere with the layout of the page. There are a range of standard sizes for banner ads - Leaderboards (long and thin), skyscrapers (tall and thin), Banners (almost square) and buttons/tiles (small and rectangular).

There are more dynamic advertising options available which include interaction in the form of videos, games, puzzles, data capture and much more. There are also more "in-your face" ad slots available which include page peels where the web-page appears to be peeling away in the top corner, revealing an advertising message seemingly 'behind' the page, page overlays where an advertising message sits on top of the web page often filling the entire browser window, expandable banners which expand upon interaction with the mouse pointer, and several others. This is known as 'rich content'.