Using Xfrom proeprty i created one registraion form with username,password,confirm password and emailid as datafields. now i want to appy some CSS and validation to that datafields. can any one help me out of this.
Xforms are rendered as an HTML Table so your style sheet CSS will need to target that table.
XForms do come with basic validation - required fields, validate as email address, etc.
If you're having issues with the default form controls and table structures, e.g. in your responsive implementations or for the sake of browser validation, then you can consider overriding the DisplayTemplates used to render the form controls and structural fragments.
Here's a good post I've been using in the past:
Alternative, Episerver Forms is the new best practice. Just as a heads up if you haven't already considered basing your implementation on that.
/Casper Aagaard Rasmussen