First, many students have no idea how to cite electronic texts. Interestingly enough, it is Web sites like this one that can help solve this problem. While a book consists of information encoded in ink on a printed page, an e-text exists as magnetic pulses over a telephone line. Discounting mishaps such as fire, flood, and theft, books are fairly permanent. As anyone who uses computers can tell you, though, servers go down and phone connections get cut.
Electronic documents can literally be here today and gone tomorrow.
As we've mentioned before, the whole purpose of a reference is to allow readers to find a source themselves. If the source itself no longer exists, this causes problems for validity and verification. One possible solution to this problem is to keep careful records. There is a special way to note if the document has no specific date. Title of document the placement of documents' titles varies.