This is the reason. I forgot to edit the code which links the pictures(Index, Files...) to their respective pages. I renamed all the pages to *.html from *.htm when I put them online. Since in the code it points to the *.htm file, it couldn't find the file, thus resulting in a 404 error.
I'm really sorry about this. I'm doing so many things I overlook simple things. You may now click on the toolbar without seeing another 404 error.
