If you enter information into this field (a random string of characters), it will add that random string of characters to your add site "submission" URL. A few software applications designed to mass spam directories look for Link Management Assistant directories based on the default name of your add site "submission" page i.e. /directory/add.html. If you enter a random string here, i.e. xg389dnlos then your new submission page will be changed to /directory/addxg389dnlos.html to prevent this.