Hi... I am relatively new to programming and I will appreciate all the help I can get from this community to understand how some things work.

My question is, how can I extract product specific data (image, price, features, discounts, etc. ) from online shopping sites (Yahoo!Shopping, Walmart, Sears, etc.) and display them on a different website. Also, is this process legal and is there a need to get prior permission from these shopping sites?

I am talking of something on lines of the 'Facebook like button' seen on many product pages, which when clicked extracts the product data from Yahoo!Shooping site and displays it on Facebook.

Please help!
Shashi.