The classid Attribute
 

The classid attribute is designed to specify the implementation of the object. When you are trying to include Flash or QuickTime files and a plug-in needs to be loaded, this value would indicate the application required to play or run the file. When you are working with Java, the value of this attribute is likely to be the Java class you want to include

Here is an example of a classid to embed a player to show a QuickTime movie: