When a browser encounters a file it can't open on its own, it goes looking for a player or plugin on the visitor's computer. It doesn't always find one. While browsers often come bundled with one or more players, software developers, always competing for market share, continually come out with new versions. Depending on the file format and extension of your multimedia file, the visitor may have to download a new player with which to view it.
Figure 18.1. If your visitor tries to view something for which they don't have a compatible plugin, they will generally see a puzzle icon or a broken image. They will also be invited to install the appropriate plugin.
On Explorer for Windows, the ActiveX control can automatically install the appropriate plugin without making the visitor close and restart their browser. This is perhaps its major positive feature, although in my experience it's much better at installing Microsoft components than components from other companies. Other browsers will alert your visitor that a new player is required and will direct them to the proper page where the necessary plugin or player can be found, downloaded and installed.
Figure 18.2. In Internet Explorer 7 (and later versions of IE 6), the program will ask your visitors each time you want to run an ActiveX control. You can avoid this alert with Java-Script (see page 292).
Figure 18.3. When a Web page in IE 7 needs a plugin that's not already installed, IE will generally offer to help to install it. In my experience, though, it is not very good at facilitating the installation of QuickTime, taking a very long time and asking repeatedly if that's really what you want to do. You might want to advise visitors of this issue and offer alternative installation procedures if you have QuickTime movies on your site.
So, to ensure that your visitors can access your multimedia files, you can: