Create a screen 100x100. Try to add 101 column or row, it will say that max cols and rows are 100x100. Open screen and press [+] to add row or column. It will create it and save it.
There needs to be extra validation for this.
Another issue with 100x100 large screens is that they not always load on IE, Chrome and Safari.
On FF it takes long, sometimes asks to stop script, but in the end it loads.
On Chromium ir loads for a long time.
On Opera it loads instantly.
Maybe some improvement can be added aswell or maybe there is no reason to make them 100x100.