Error while editing style.css and index.php

Hi,

I have recently installed my blog at environmentpress.in and am trying to make changes to my style.css document but constantly keep getting this error

You need to make this file writable before you can save your changes. See the Codex for more information.

I have already visited my ftp and ticked the permission to read and write and execute/search (I do not have the option for numerical values) and am at a loss of what to do next..

Please help,

Thanks,

Ekta