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you’re right in suspecting that testing sites in safari on windows isn’t enough. Macs render fonts differently (arguably more accurately) and these subtle differences can affect some designs. Browsershots is a good site, but if you are serious about web design (in that you wish to do it professionally) then it might be worth checking out eBay for an old mac. A g4 capable of running tiger OS can be picked up for around Â£50.