have a question,

i choosed “To use Comodo Secure DNS server only for Comodo Dragon browser. All other applications will be connected through your default DNS server.” during the installation of comodo dragon,but also connected my computer to the internet through a router which was setted to use the dns provided by my isp.so which dns server would i use at last if i use the comodo dragon later after the installation,the comodo secure dns server or the server provided by my isp according to the setting of my router?

it will use comodo dns in dragon only since that is what you selected. if, for whatever reason, comodo dns cannot be used dragon will use the dns setup on your router.