Quote by Dazzy: Thanks guys but I already had the images in the interface folder.
I have also upload the xlib thing to my root directory
You have two problems:
1) You're X library paths are incorrect in your header.thtml file.
2) arrowLink.href = 'javascript:toggleBlocks('right')';
There should be backslahes to escape the inner quotes. That is in your rightblocks.thtml file. Your leftblocks file is correct, so you can use that to compare.