I'm pretty sure that my last bank holiday was ruined by Internet Explorer 8, and now that our clients have dropped that from their supported version list, its younger brother has stepped up to the plate to try to ruin this bank holiday for me. A stylesheet which works fine on Firefox, Safari, and Chrome (and even works tolerably on IE8, incidentally), inexplicably fails to apply a huge number of styles on IE9. This is a delightful thing to find out essentially 1 working day before a planned release. We can of course go into some life lessons learnt, but they might come out a bit on the grim side (i.e. never trust anyone else to check anything, you will always have to fix everything yourself). So nuts to that. This is about technical lessons learned. Here are some things I've found so far: This project has some pretty terrible CSS, a product of stuff being layered on top of other stuff forever. Code decays, and CSS decays particularly fast, it seems. When you look at the...