SevenCubed - 5:15 pm on Oct 21, 2013 (gmt 0)
I advocate the use of em units as it avoids issues with small but high res screens (e.g. retina) etc.
Agreed very much. When you consider that google has 200+ items of criteria to measure worthiness of a website and bing claims 2000+ it's obvious one needs to pay attention to something like ems as units of measurement due to rise of mobile popularity.
I've recently had to rework some of my older websites and used the opportunity to revamp everything to ems for units of measurement. It has strong mobile benefits. Got last one scoring 100% on both desktop and mobile as per google Page Speed Insights tool.
The website optimization results in a universal site with a uniform experience across all devices and there is benefit in that (as one of many onsite factors) for boosting SERPs.
@UK_Novelist your website isn't overly complex, it might be worth considering bringing it up to standards of HTML5/CSS/SPRITES/EMS-FOR-MEASUREMENT/RESPONSIVE-FOR-MOBILE.
If you're attached to the effect of frames you can substitute it with CSS Layers for an equivalent user experience.
Throughout that process you'll probably resolve your other dilemmas that you pointed out too.
There are sources of basic free responsive design templates out there that you can learn from and adapt for your need.
Overall it would be a worthwhile effort because you'll gain higher placement in search results.