This should probably go into the question and answe thread, just so you know until next time.
What I usually do is stand on the last row perpendicular to the right side of the skulltula-thing. Press B, turn around, press Z, climb down and hold down, press A and immediatley after hold up.
Now here's the timing: If link turns around and starts backwalking directly, then climb down 2½ steps before you press A
If he takes a step, then climb down 2 steps before you press A
If he takes two steps or more, you'll probably have to do it again because he'll probably grab the ledge rather than the vines...
Good Luck