In environments where you don't have direct control over the network CD writer it can happen that someone else (think of an user without webCDwriter experience) puts in a CD while webCDwriter is waiting for your CD. To avoid at least the mixing of private data of two users on one CD the webCDwriter write protection was invented.
If you know there is already a session on your CD, you may instruct webCDwriter e.g. to reject all empty CDs without a table of contents. If an empty CD is put in, it will be ejected after a short test and you have still the chance to put the correct CD in.
Give a user ID to protect you CD within webCDwriter. If you want to write to it in the future, you will have to give the same ID in the above section or webCDwriter will reject it.