How to fix a 3g & wifi connection on iphone 3g.. there was a time that i already connected to the internet specially on wifi but in a minute the pop-up wants me to connect to the wifi connection first

not very clear about your issue... please put in more details

thanks to amdriyaz to your concern..
as i've said when my iphone 3g connected to a wifi connection and enjoying to surf the pop-up comes in 5mints or more, it say that i need to type the password to connect. it means my iphone not connect thru wifi. what's happen & how to solve it to continually connected to wifi..