Hi Kumar,
YES it does.
You do use the parameter ~ITSMOBILECSSINCLUDE so that your custom CSS file is being used?
It is recommended to copy the standard "mobile.css" file in the service 'itsmobile' and modify it.
Perhap's this is the reason your customized .css file is creating this effect?
See also the ITSMobile WIKI: Service Parameter and Settings
Regards,
Oisin