Thanks guys, I think I've got it. I deleted files in tmp folder now it seems working fine. I thought there was no limit on disk space usage.
but I do have another big problem, i can login no problem, but when I try to get in file manager, it page shows up and on the left it says collapse all...
Thanks for replying, actually, I tried both FTP and Cpanel, many many time, either the new file could not override old file or it Chang to 0bt after I delete the old one and upload the new one. And the index.html I was trying to upload is only a 10k file. Thanks