I'm using CodeIgniter framework for PHP. It takes that index.php ought to be there in whatever url i type. How do you prevent this? Can anybody provide us a simple .htaccess file which will unconditionally map it to index.php so user does not need to types each time?

Thanks ahead of time:)

Use a .htaccess file (or better apache.conf) to forward all demands to index.php with mod_rewrite:

Options +FollowSymLinks
IndexIgnore */*

<ifmodule mod_rewrite.c> 
RewriteEngine on

    # if a directory or a file exists, use it directly
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d

    # otherwise forward it to index.php
    RewriteRule . index.php
</ifmodule>

In case your request is http://www.example.com/controller/view, than $_SERVER['REQUEST_URI'] is /controller/view. You are able to interpret it with Regex or simply by splitting string: explode('/',$_SERVER['REQUEST_URI'])

You have to look at this http://codeigniter.com/wiki/mod_rewrite/ Because you'll should also create a small code change (in step two) not covered in Svens answer.