This is something I hardly ever do. I don't like the leap of faith and hate the faff of returning things. I don't mind going to actual shops every now and then and I live in London so realistically have plenty of choice.
One of the reasons I hate online clothes shopping is that it can take one or more clicks to even find out what fabric the garments are made of! Clicking through a blouse on Gap site today and I still don't even know what the bloody thing is constructed out of? Shouldn't fabric type be more or less the first word in the description?