Hi Nageswari,
In my opinion there are 2 ways you can go about doing this:
1 - You can use a module like Dynamic Login that will allow you to format the way you want your login to look like with their template engine;
2 - Or you could just CSS format the current default DNN login by accessing labels and input via their IDs and place some CSS format on them. You could have an entire login.css file create for your login page. This is a bit hard and can be tricky to set it up. It will also put some constraints into what you can do.
I tend to think that #1 above is the best approach.
Best regards,
Aderson