Wouldn't it be lovely if we didn't have to concern ourselves with the html? So far, it remains Not Possible to present a single html object tag that provides sufficient guidance for both Firefox and IE, for instance.
The way to show active content using X3D hosted on a typical html/xhtml web browser is to use simple ecmascript to evaluate a basic browser capability check and generate a specific object element based on browser object implementation preferences and capabilities....
Open Standards for Real-Time 3D Communication
A nonprofit organization that develops and maintains the X3D standard--a 3D file format and runtime specification that is open, royalty free and ISO ratified for transmission of 3D data over networks.