User:BCube/Works in progress/Hover ad

Hover ads are a special type of pop-up ad created using Dynamic HTML. The advertisement is usually a flash animation superimposed over the page, making it "hover" over the content, usually obscuring it.

Background
As pop-up ads generally attract the user's attention, they became a popular form of Internet advertising. The first Internet pop-ups were generated using JavaScript, and displayed the advertisement in a new browser window. These popups were easily blocked by pop-up blockers, such as the Google Toolbar.

In order to circumvent these pop-up blockers, some advertisers started searching for alternate methods to display content that would attract the same attention as a pop-up window. One method developed was to use Dynamic HTML in order to display advertising content above

Technology
Hover ads are developed around several web browser technologies but in the centre of their realisation is utilised DHTML, a technique where JavaScript modifies the content of the page. Using JavaScript, certain levels and objects of the browser’s DOM are manipulated to produce window-like visual DHTML elements representing hover ads or hover ad windows. The basic attribute used is a CSS HTML element attribute - position. Modern browsers implement cascading style sheets in order to separate presentation from content. The CSS technology also enables the JavaScript content of a web page to manipulate programmatically CSS attributes of various HTML elements constituting the web page's content. The first movable HTML elements were introduced in Netscape 4 with the so called layer technology. Now it has been deprecated. Hover ads tend to be very hard to block by popup blocking software because the hover ad window is an integral part of the HTML content of the web page. Thus a software filtering the content has no algorithmical means of recognizing and removing parts of the content, either descriptive or procedural, that create, populate and manipulate the hover ad's window.