I do too. I don’t aim for ‘pixel perfect’ but the page should at least be USABLE.
Given that until two to three years ago 5.5 was the latest version available for windows mobile, and 6.0 is still the most recent available for same…
Using simple techniques and swinging an axe at “Gee ain’t it neat” nonsense that has no business on websites in the first place (see 99% of what people vomit up using jquery) you can build sites quickly that work just fine back to 5.5 for little to no extra effort… that work just fine right through to the latest and greatest flavors of every browser.
Not being able to do so easily either comes from broken methodologies, outdated coding techniques, or jumping the gun on technologies not ready for prime time (CSS3)
… or should never be adopted for use in the first place being a crippling train wreck of bad ideas setting coding practices back a decade or more. (HTML5)