I need to click on a button in header then overlay will show like Sencha Touch:

how to do this overlay with jQueryMobile in the same page
JsFiddle Example:
http://jsfiddle.net/ReMZ6/184/
Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
Currently this overlay support for dialog is not available in jquery mobile.But it is expected to come in future versions.They have put up a demo of how that feature is going to be in this url – http://filamentgroup.com/tests/popup/docs/pages/popup/index.html
For the time being you can use the following code to achieve something similar to what you need:
A demo here – http://jsfiddle.net/K3Tpu/
This is just a rough draft only and there might be some issues.
Let me know if that helps.