See http://stackoverflow.com/questions/433907/how-to-link-to-apps-on-the-app-store
To send customers to a specific application via the browser: http://itunes.com/apps/appname
To open an app in the app store (e.g. for a rate this app link) use: itms-apps://itunes.com/apps/appname
For app names with spaces simply remove the spaces.