How can I see in the App store whether I am working secure I wanted to buy some small application from the app store, it asked for my credit card information, but I was unsure whether we were working in secure mode.

How can you see, during payment, whether your are working in secure mode or not ? (like the green colour in Internet Explorer).
Assuming you were purchasing through Android Market (App Store is iPhone), credit card payments are handled by Google Checkout.  (More info: http://market.android.com/support/bin/answer.py?hl=en&amp;answer=105916 )

Google Checkout API is secure even though you won't see an HTTPS indicator like you would for SSL-enabled sites in a web browser (e.g. the green location bar in Internet Explorer).