How to create customize website?

It is accomplished by using jquery and css. So I suggest you to read the jquery and css very carefully. Bacause I can provide a code for that but may be it will work with your planning. So I would like to suggest you to study jquery and css for change design dynamically. You can do this from code behind but it will be so bulky. So it will not so good idea in that case

Ok. Now create 3 tables into database. One for store the html designs of templates at varchar named "TemplateDesignTable". 2nd for store information of your users named "UserInfoTable". And 3rd table to store the records of which users choose which template named "UsersTemplateInfoTable". Now at first take the printshots of ur templates and show them into a grid. And when user select any template, on save button click you just save the information of template and user id into the 3 table. Your site will be ready

Hi, can you please explain little bit more clearly

Hi, this can achieved in various way depends upon your requirement. It can be done in very modern way also, say user can create website simple drag and drop control into the website or may be user have to choose the controls without drag and drop. So many ways are their to do that. At first tell me your idea, planning to do that

If SharePoint is installed in the environment - you can use SharePoint.