I can assure you that the level is possible, but if you can provide a screenshot of where exactly you are stuck, I'm happy to give a hint.
Here are some more general tips:
- The length you press the jump button for determines the height (you do not need to hold the button down for very long to get the maximum height jump though).
- Make sure to use all the space you have for very tricky jumps: if you time it just right, it is possible to leave it to the very last second before jumping. A run-up is useful, but the player has a relatively fast acceleration, so you don't need more than one or two blocks to get up to full speed.
- The web version of the game can sometimes have a slight delay between pressing a key and it responding. I'm not sure why this is, but I'd recommend downloading the game for better performance (this problem might make it very difficult to perform jumps which require you to go right to the edge of the platform) .