It means you must have a working web site, be a member for 7 days or longer, be using at least one-half of your initial allocation of web space and abide by the Terms-Of-Service (TOS). A link to the TOS can be found at the bottom of each page.
There is a file in my file system in .cagefs/tmp named phpXgEUgT that is about 310 MB (3/5 of my disk space). Can I just delete and recreate this file?