[Description] Attributes of this type identify the allowable content type(s) of an associated URI (usually a value of another attribute on the same element). At its most general, it is a comma-separated list of media ranges with optional accept parameters, as defined in section 14.1 of [ RFC2616 ] as the field value of the accept request header. In its simplest case, this is just a media type, such as "image/png" or "application/xml", but it may also contain asterisks, such as "image/*" or "*/*", or lists of acceptable media types, such as "image/png, image/gif, image/jpeg". The user agent must combine this list with its own list of acceptable media types by taking the intersection, and then use the resulting list as the field value of the accept request header when requesting the resource using HTTP. For instance, if the attribute specifies the value "image/png, image/gif, image/jpeg", but the user agent does not accept images of type "image/gif" then the resultant accept header would contain "image/png, image/jpeg". A user agent must imitate similar behavior when using other methods than HTTP. For instance, when accessing files in a local filestore, might cause the user agent first to look for a file logo.png ,and then for logo.jpg . If a value for the content type is not given, "*/*" must be used for its value. For the current list of registered content types, please consult [ MIMETYPES ]. [Data type] 
ContentTypes