Unix uses the "chmod" command to change the permissions of files. Permissions are broken down into three access levels - those of the owner, his/her group, and the "world" (everyone else). In order for the web daemon to serve your files, they must be "world" readable. You might want to change the other permissions for various reasons, so here is a chart. You can only change permissions on the files which you own (in your home directory).
Owner Group World  
rwx rwx rwx chmod 777 filename
rwx rwx r-x chmod 775 filename
rwx r-x r-x chmod 755 filename
rw- rw- r-- chmod 664 filename
rw- r-- r-- chmod 644 filename
r = Readable
w = writable
x = executable
- = no permission
Here is one more way of looking at it:

400        read by owner
040        read by group
004        read by anybody (other)
200        write by owner
020        write by group
002        write by anybody
100        execute by owner
010        execute by group
001        execute by anybody

To get a combination, just add them up. For example, to get read
write execute by owner, read execute by group, and execute by anybody,
you would add 400+200+100+040+010+001 to make 751.