php - why i have to give port number manually in the browser -

i have changed port in wamp when run wamp got

error 404-not found

all time have give port number manually 80 t0 81

"http://localhost/phpmyadmin/" "http://localhost:81/phpmyadmin/"

how solve problem. did not install skype. have installed vs2010,sqlserver2012

i have done following things wamp--

changed port 80 81 in apache=>httpd.conf file

because convention http protocol if no port added, 80. if port 81, without specifying port, use 80 , wamp won't accessed. try using port @ 80 , accessing http://localhost:80/phpmyadmin. you'll find can access same http://localhost/phpmyadmin.