Thanks a lot for your comments guys
I just did the Ankle Flexibility Test from Eric's post. I didn't warm up or anything, but it didn't say if I should. I stretched my calves between the second and third attempt which gave me maybe half an inch more. At 19.25 inches my ankle flexibility is poor. You could say very, very poor.
My stance is as Eric suggested it should be. At gym they suggest our feet be shoulder width plus half apart, and it may help to turn our toes out slightly, so I do. I can bend my knees to about level with my toes, but they don't seem to go further.
My hips are pretty flexible I think. I had a look at the Hip and Trunk flexibility test on the same site. They had me do that test at gym at the start of the year. I'm not sure what I scored, but I recall my trainer's comment - "That's way too flexible."
I should mention that I was doing other squat type of exercises prior to my program changing at the start of the week. I used a machine that was only referred to as the Forza Squat. It's plate-loaded and you hold onto two hand grips (which move with you) and lower yourself into a squat. Then I would use a squat press machine, followed by a hack squat.
Perhaps I should also mention that we are taught that the angle of our back, in comparison to the floor, should not change throughout the movement, ie. we should still be tipped over when we come back up, rather than standing up straight.
I've done a more thorough reading of the "How to squat" article. I'm confused by this: "The shins should be a close to vertical as possible throughout the entire movement." If that is so, then what's my problem? They're verticle when I stand...flexibility of my ankle wouldn't affect it at all. In "squat.jpg" his shins don't look vertical, and I think shins in most pics of squats I've seen aren't...
0311, Don't you worry, I take everything he says with a grain of salt. I plan on asking two of the others. One of them is a former IFBB title holder. He should know some stuff!
I'll have to read the other things tomorrow, as it's zzz time. Thanks for your help!