A template can be made from scratch or converted from a pre made design.
There are many templates not specifically made for Joomla at sites like freecsstemplates that can be converted to a Joomla template.
Adobe Illustrator and Photoshop layered files can be converted to Joomla templates. Joomla 1.5 templates can be converted to Joomla 1.0 and vice versa.
When making Joomla templates I strive for fast loading table-less design that meets XHTML and CSS validation requirements.
Please note that adding extensions can sometimes break XHTML validation. If you have this problem it can be fixed. Sites that validate rate higher in the SERPs.
Joomla Extensions often need to be styled and designed to match an existing template. Pre-made Joomla templates often need some tweaks, or a custom header inserted.
Templates are tested on these browsers for compatibility: Windows: IE7, FireFox | Macintosh: Safari, FireFox, Opera
