am getting this error :

Error: headers already sent in index.php on line 3.
Stopped at line 759 in joomsef.php

please advise as the main website is ok at www.bobbytours.com
any other page doesnt open and gives the above error

Hello,

it seems you have some invalid characters in the start of your index.php file.
Check that it starts with <?php and there are not characters before that -- you should just some plain text editor to check it, as many editors do not shown special e.g. UTF-8 characters thay may got there, if someone has been editing the file.