The structure of the VRML document is a header, scene graphs, prototypes, routes and comments. It's very important to put the header on the first line of all of your documents preceded by a # character. When the browser starts reading them it will search for the VRML's version you used, so get it right otherwise you might not get a correct response from the browser.
For version 2.0: #VRML V2.0 utf8.
And for version 1.0: #VRML V1.0 ascii.