<a href="' . $_SERVER['PHP_SELF'] . '?month=' . $last['month'] . '&year=' . $last['year'] . '" style="text-decoration: none;"><<</a>
I'll explain this one and then we'll see if you can figure out the next one okay?
$_SERVER['PHP_SELF'] is simlpy the name of this script. Anytime you want a link of form to point back to the script it is generated from you should use this so that moving the file doesn't break the link or form.
$last is an associative array in the code
$last['month'] is either the name of the number of last month (It's impossible for me to tell which without seeing the code or a working version of the script)
$last['year'] is the number of the year.
So this would create a link that looks like this <a href="somepage.php?month=7&year=2003>&lt;&lt;</a>
Which would look like >>.