Presentation
Microsoft PowerPoint XP file
seminar2003.ppt
Website and presentation by James Barker, 3rd December 2003.
Some sites give the user the option to switch style sheet, to ahieve accessibility (in large text versions), or to give the site a completely different layout or look (or skin) - this could be well employed on entertainment or children's sites.
This example from meyerweb.com demonstrates the potential of switchable style sheets.
Many gateway sites use portal technology to allow the regular user to personalise the content they see on the site home page, or even the colour scheme.
This is a way of giving the user control, but within your limits.
User defined layouts
User-selected CSS
Meyer Web.com