* For generic files such as html or images, etc you usually need to set 644 permissions. It is because "nobody" needs to read the file, and thus the file should be readable by others, hence 4 (read only) permissions for both group and others. For yourself you need a right to read and write (hence 6) to the file.
* For scripts you need 755 rights. The script should be executable by "nobody". The script file should also be readable by "nobody", as the file is interpreted by an interpreter such as Perl and therefore must be readable. Thus it must combine read and execute permissions for "others", as "nobody" belongs to "others" group. For yourself you need to have also write access, getting 755 as a result. "