User Agent (browser) appears to be -
MOZILLA on Windows (Gecko based)
SEA MONKEY on Windows (Gecko based)
FIREFOX 2 on Windows (Gecko based)
FIREFOX 2 on OSX/Mac (Gecko based)
FIREFOX 3.0 on Windows (Gecko based)
FIREFOX 3.5 on Windows (Gecko based)
FIREFOX 3.6 on Windows (Gecko based)
FIREFOX 3.7 on Windows (Gecko based)
FIREFOX 4.0 on Windows (Gecko based)
FIREFOX 5.0 on Windows (Gecko based)
FIREFOX 6.0 on Windows (Gecko based)
FIREFOX 7.0 on Windows (Gecko based)
FIREFOX 8.0 on Windows (Gecko based)
FIREFOX 9.0 on Windows (Gecko based)
FIREFOX 10.0 on Windows (Gecko based)
FIREFOX on Windows (Gecko based)
FIREFOX 3.0 on OSX/Mac (Gecko based)
FIREFOX 3.5 on OSX/Mac (Gecko based)
FIREFOX 3.6 on OSX/Mac (Gecko based)
FIREFOX 3.7 on OSX/Mac (Gecko based)
FIREFOX 4.0 on OSX/Mac (Gecko based)
FIREFOX 5.0 on OSX/Mac (Gecko based)
FIREFOX 6.0 on OSX/Mac (Gecko based)
FIREFOX 7.0 on OSX/Mac (Gecko based)
FIREFOX 8.0 on OSX/Mac (Gecko based)
FIREFOX 9.0 on OSX/Mac (Gecko based)
FIREFOX 10.0 on OSX/Mac (Gecko based)
FIREFOX on OSX/Mac (Gecko based)
CAMINO on OSX/Mac (Gecko based)
EPIC on Windows (Gecko/FF based)
DOCZILLA on Windows (Gecko based)
K-MELEON on Windows (Gecko based)
NETSCAPE 8 on Windows (set as Mozilla)
NETSCAPE 8 on Windows (set as IE)
OPERA 9 on Windows
OPERA 10 on Windows
OPERA 11 on Windows
OPERA 7 on Windows
OPERA 8 on Windows
OPERA 8 on Windows (set as IE)
OPERA 8 on Windows (set as Mozilla)
OPERA 9 on Windows (set as IE)
OPERA 9 on Windows (set as Firefox)
OPERA on Windows
INTERNET EXPLORER 5 on Windows
INTERNET EXPLORER 6 on Windows
INTERNET EXPLORER 7 on Windows
INTERNET EXPLORER 8 on Windows
KONQUEROR 3 on Linux (WebKit/KHTML based)
KONQUEROR 4 on Linux (WebKit/KHTML based)
SAFARI on OSX/Mac (WebKit based)
SAFARI on Windows (WebKit based)
SAFARI 3 on OSX/Mac (WebKit based)
SAFARI 4 on OSX/Mac (WebKit based)
SAFARI on iPad/iOS (WebKit based)
SAFARI on iTouch/iPhone/iOS (WebKit based)
GOOGLE CHROME on Windows (WebKit based)
GOOGLE CHROME 2 on Windows (WebKit based)
GOOGLE CHROME 4 on Windows (WebKit based)
GOOGLE CHROME 9 on Windows (WebKit based)
GOOGLE CHROME 10 on Windows (WebKit based)
IRON 4 on Windows (Chrome based)
IRON 6 on Windows (Chrome based)
All the pages are coded as XHTML 1.0 Strict and are served as text/html rather than as
application/xhtml+xml with the .xhtml file type using content negotiation on the server
(which true xhtml requires).
UPDATE:
Not using HTML5 yet but XHTML 1.0 Strict pages work OK in browsers optimised for HTML5 and
will be treated as similar to XHTML5.
Efforts are now focused on satisfactory working in mainline modern browsers that support HTML5
eg: Chrome, FireFox , Opera, (if Edge works fine but I'm not overly worried anymore).
Legacy browsers (generally pre-HTML5 may or may not work .......)
The site is now responsive with device specific stylesheets.
mobile
desktop
In general the mobile style will cover iPhone/phone aspect ratios and the desktop will handle the normal desktop and iPad/tablets.
Desktop mode will start at 600px viewport width.
Some samples of device viewports -
iPhone 5S/SE Portrait mode:
HERE
iPhone 6/7/8 Portrait mode:
HERE
iPhone X/XS Portrait mode:
HERE
iPad Mini Portrait mode:
HERE
iPad Mini Landscape mode:
HERE
1080P HDTV:
HERE