Common Mistakes
Taking off with your jumping foot not directly underneath you.
If you takeoff with your jumping foot too far back, you will direct a lot of momentum forwards instead of upwards. Most websters done this way will land too low or in a crouched position (or not at all).
If your take off foot is too far in front of you, which is far less common, you will cancel out a lot of your flip. You get a good amount of vertical momentum but next to no horizontal, which is needed for the flip and the frontswing. Most likely you won’t make it around completely or you need to put your hands down before you land.
Opening up too early
If you have this problem, all I can tell you is to really force yourself to stay tucked for the whole flip first. You might want to try this on a softer surface if you feel insecure about it. As you get more and more comfortable with this trick, you will develop more air awareness and then you can learn to open up as soon as you can spot forward again. That way you can stand out from the trick in an upright position.
Not pushing through all the way when you jump
Jump UP with full extension. Everything should be straight in the moment you takeoff. From your toes all the way up to your hips. If you take off too early, you’ll eliminate a lot of height. You can flip around with a good tuck and swing, but you will very likely land too low in a crouched position or even on your butt.
Spotting the ground
As you take off, you should spot in front of you. When you flip, you tuck your chin and you don’t spot anything in particular. After the flip you spot forwards again to open up. If you’re learning the webster from an aerial first, you might have develop the habit of looking at the ground the entire time in your webster as well. This can result in two different things. First it could make you flip more sideways, like an sideflip. I’m still making this mistake out of habit a lot of times. However it can also result in an arched back webster, which is actually a front aerial. It requires a lot more back flexibility and doesn’t rely on a tuck. If you don’t have the flexibility, you will just fall on your back or put your hands down to prevent you from crashing onto your neck.
Hips are not square
Your hip positioning is very important to keep your webster as a frontflip. If your hip is not staying perfectly square facing the front, you will flip on a sideways axis, making it a little bit sideflip-ish.
Treating it like a normal punch frontflip
It is technically a one-footed fronttuck but it works way different. The fonttuck is entered with a punch or pop setup, while the webster uses a frontswing. Many beginners try to enter the trick correctly and as soon as they jump off, they kill all the swing momentum and just try to tuck in after the jump. The flip will usually be too slow or not high enough. Treat the webster more like an tucked forwards aerial. Also don’t enter the swing with your arms raised all they up above your head (like in a frontuck). Swing them more like you would for an aerial.