I'm always trying to optimise and refine my sites. I often mess around with the CSS files, the HTML templates, and the variables to tweak the design and layout.
The problem is, you have to click all over your site after a change to see what effect it had. It's easy to miss something.
My solution was to create a dummy article that contains examples of all sorts of HTML tags - normal text, headings, code samples, blockquotes, my colour variables, and other important variables.
I named this article 'test', so that it publishes as 'test.html', and then set my FTP preferences to display 'http://www.sitename.com/test.html' as the preview page.
So after each change, I just hit Publish and then click on Preview. Most types of design change are visible at a glance.
If you want to check it out, here's my Design Test Page.
To prevent this page from showing up anywhere on my site (since it's not really for site visitors to see), I put '(NFP)' in its keywords field. All my CityScript loops exclude NFP articles from lists of links — see the tip at the bottom of the Short Tips page for more information.