Changing existing Web site design

For my Free online articles directory I plan to change its layout like placing of the content mainly the navigation part. as of now I'm getting a good traffic from google but bit scared before I change the layout as I am not sure how its going to effect my site ranking in google.

 

dont change url and its name otherwise search engine understand its new page and remove old page

 

what if I change the pages name. if fact I was thinking to move from .net to php how would that impact?

 

Yah it will just update your site but still the same, it will only change once you decided to change your url all your source and links everything will going start all over again.

 

If you are using the same link navigation as old one then it will not effect in Google...