SmartNavigation is a feature provided by asp.net. When enabled this makes sure your pages are shown smoothly and last position of cursor location, scroll etc are restored effortlessly.
Why this feature deserves a mention here?
Because of the problems it creates. It isn’t very reliable because of the following reasons.
Smartnavigation removes CSS after postback
This was the sole reason for blogging this. Yes smartNavigation strips off css after a postback.
Solution - you need to explicitly specify the path of css as absolute path instead of relative path. You can keep it dynamic by adding some server side code as below LINK href=''< =Request.ApplicationPath %>/Styles/Sanjay.css''
Microsoft's documentation of SmartNavigation
If you still wish to use smartnavigation on other browsers take a look at this code project (Free source) Crossbrowser SmartNavigation Alternative II
Conclusion: Use this feature only when you are sure of your audience using latest IE (at least IE 5) only. And make use of it when its absolutely necessary to make your application work better. And do take care of css paths etc.