I need help to get Latitude and Longitude dynamically and longitude from a user entered zip code. so that I can work to show the store address in this zip code area.
Google starts some kind of geocoding, you have to check it out, it can help you http://code.google.com/apis/maps/documentation/geocoding/
http://code.google.com/apis/maps/documentation/geocoding/
There are some requirements for this, for example, you need to register your google account, but it is very simple, and you need to pass some parameter that is described there.
JSON XML .
You have not indicated which country you want to do this in, but you can use the GeoNames API for postalCodeSearch.
postalCodeSearch
For example (XML and JSON responses respectively)
http://api.geonames.org/postalCodeSearch?postalcode=90210&username=demo http://api.geonames.org/postalCodeSearchJSON?postalcode=90210&username=demo
Going a little deeper, you can get a JSON-encoded object from google from the following URL:
http://maps.googleapis.com/maps/api/geocode/json?address=ZIPCODE&sensor=false
just replace the ZIPCODE with the zipcode you need, and it should return you a json object with latitude and longitude coordinates.