Correction Appended

Where was the Flash?

Web designers  and a fair number of Web users  noticed something missing from Steven P. Jobs’s demonstration of the Apple iPad Wednesday. On some of the Web sites he displayed on the tablet computer’s screen, blank squares appeared where video or animated content would normally be displayed.

The holes, observers correctly assumed, meant that the iPad would not display videos, animations or any other features created using Flash, a type of multimedia software made by Adobe. Flash is one of the world’s most ubiquitous applications, appearing on 98 percent of all computers. YouTube videos run on it. It is what animates millions of graphics and advertisements on Web sites around the world. Adobe says the technology supports nearly 75 percent of video on the Web and 70 percent of online gaming sites.

But Apple’s support for Flash has been flagging. While Flash is present on nearly every Apple desktop and laptop computer, the company decided that Flash would not be used on the iPhone. Apple has argued that the Flash technology is too slow and unduly taxes laptops and netbooks. The company also has concerns over Flash’s vulnerability to viruses and other malware, as well as the way Flash-based content can voraciously consume battery life.

Adobe, unsurprisingly, disagrees  and has its own theory about why Apple remains hostile to Flash. Adrian Ludwig, group manager for the Flash platform product at Adobe, said he believed Apple’s opposition was a way for the company to control its iTunes system. “I think it’s pretty clear that Apple wants to regain control of the content consumers see online and the content Apple offers for their devices,” Mr. Ludwig said.