Site definitions have moved from config to database. http://world.episerver.com/Documentation/Items/Upgrading/EPiServer-CMS/75/Breaking-changes/
You can set the start page by going to admin mode -> config -> manage websites -> edit web site
Thanks for your solution.
I have created a CMS site with 4 pages in EPIServer. Now I want to set the page with id '5' as the start page. in episerver.config section I am not finding the sitesettings section . I am developing the MVC application template provided by .NET. But not getting any option for setting pagesstartid. Where to set taht in episever.config file.