I want to make an app which will show a feedback form at the end when the user hits submit the form should be sent to my email id in .txt or .doc format. My problem is this feedback form submission where mail will be sent should be uniform on Android, iPhone and windows phones. I want to implement this using HTML 5. What are the challenges i should keep in mind while implementing this?
If you want to write a HTML5 application, then consider using PhoneGap, it provides a standard set of JavaScript APIs for using native phone features (camera, contacts ...) across a wide range of smart phones. Windows Phone 7 support has been added recently.
One problem you will face is sending the emails, there is no common API for this function. My advice would be to use HTTP POST to send a message from your HTML5 application to some server-side component that will actually send the email. You will of course have to consider security here, you do not want to expose a service on the web that allows anyone to send emails!