Quote solostrike's article: "The item effects section is the main part of items. This section defines what your items will do when the player decides to use them and what page the player is taken to. You are allowed to have multiple effects and different page use and destinations. When adding an item effect, you need to select the link “Add effect” and it will open a window. There will be two boxes. Both boxes contain pages within your game. The first (top) boxes function is to define what page the item will be used on. The second (bottom) boxes function is to define where the player will be taken to when the item is used on the specified page above. In smaller words, if used on page selected in first box, go to page selected in second box.
A default effect is when the item is used on a page not specified in the item effects section. A default effect happens like so: The player uses a credit card item while the page says he is in the washroom. Now, I do not think there is anyone out there who uses their credit card to purchase something while in a washroom. If you have a default effect, the player will be taken to a page specified in the default effect section. For example, “You cannot use the Credit Card right now, try at another page”. The reason I did not say “You cannot use the card in the washroom” is because since it is a default effect, whenever it is used in the wrong place it will be taken to that page."
From this, I'm pretty sure you don't need to set where and Item won't work, only where it will work.
