If this option is set to true, all URLs returned from the MCFileManager will be relative from the specified document_base_url if it's set to false all URLs will be converted to absolute URLs. This feature can not be disabled since MSIE and FF modifies the URLs of DOM objects by them self so TinyMCE tries to solve this problem by reconverting them. This option is set to true by default.
Example of usage of the relative_urls option:
tinyMCE.init({
...
relative_urls : false
});