When editting a Content Management System (i.e. wordpress or drupal etc..) or any web file (php, asp, html, css etc) it is essential to have the correct permissions to access and change that file.

The most common way to do this is using a File Transfer Protocol (FTP) interface such as smartftp or filezilla. First browse to the file you need to change then select it and right hand click (or apple click if you are on a Mac) and choose either properties, file attributes or CHMOD. This will bring you to an options menu that lets you change who can access the file either with a check box system and/or by typing in numbers.

There are 3 levels of user, owner, group and public. and each of these levels can have 3 options with the file; read, write and execute. In Unix these levels are represented by numbers (0 for no access, 4 for read only, 6 for read and write and 7 for everything). So 644 would mean the owner can read and write, group access is read only and so is public access. 777 would be all users can do anything they want – this is generally not recommending as it opens the file up to be editting by anyone.

 Generally is you are the owner you need at least read and write access and maybe execute, but group and public access rarely should be more than just read access.

For a look at how to do this in the Unix command line click here