What causes a squeak on front wheel?

Mainly its because of warn down break pads, they have built in 'squeakers' to warn the driver they need replacing. usually quite loud especially when turning corners.

new pads can also squeak they just need time to wear in, check if your pad has copper grease on the back aswell, this helps. or if you've used 'back to black' etc on your tires and got some on your disks, that squeaks.

wheels can also squeak from lose wheel nuts strangely enough, i had this problem when getting new alloys and not fitting them properly.