How to Undo automatically connect in wifi in NOTIFICATION AREA

That is normal, and happens when you tick it once, Windows remember to connect to it but hides the checkbox. You can undo that by entering network center (at the bottom of the popup) => manage wireless networks => right click on the network => remove.

This will make the option reappear, and no longer auto-connect to that network again.

Ok brother thanks..but i fear if i remove that particular wifi network will that appear again in my wireless network and connection list in notification bar??? I MEAN WILL I BE ABLE TO CONNECT IT BACK AGAIN???

Yes, there will be no problem connecting again.
The list I pointed is just where Windows stores all the "connect automatically" networks you tick and their passwords you type. By deleting you're instructing Windows to not connect it automatically again, hence it again gives the option to do so.
But the network itself will be accessible as always was on the popup on the tray and you'll be able to connect normally.

Thanks Brother.THanks a lot