How do i validate through jQuery and display error message without postback?

Hi,
 
I have two Textboxes(For Instance txtEmail1, txtEMail2) where we allow the user to enter their email address. txtEmail1 will be in Enabled condition and txtEmail2 will be in Disabled condition when the page loads first time.
How do i validate txtEmail1 text should be Email through jQuery?
If he/she enters right Email format then it should enable the txtEmail2 otherwise, it should display proper error message next to txtEmail1. How will we do this?
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