One of the things that took the most work to get right was the thickness of the graph lines.  Because of the nature of the graphs, it was an absolute necessity that the lines be drawn with antialiasing enabled.  PHP’s interface to GD (or perhaps it’s GD itself?) ignores the line thickness setting when antialiasing is enabled.  The solution I eventually settled on is to, more or less, draw several one-pixel-wide lines next to and on top of one another to get the appearance of a thicker line.

As an aside, I’m using the technique mentioned here for permanently redirecting the old URL to the new URL:

… if you actually moved something to a new location (forever) use:

<?php
 header("HTTP/1.1 301 Moved Permanently");
 header("Location: http://example.org/foo");
?>