About Skins and HTML Templates (as that is what you
seem to propose)
I had a few of my webpages running using Fast Template
http://www.google.com/search?q=fast+template (a few tutorial +
modifications can be seen on google)
I don't really like it anymore, but it may be worth a look.
The way you handle it is, making an external template file which is
basically html-code with {SPECIAL_TAGS} in curly brackets which you can
replace from your code.