>We users simply don't expect that buttons will suddenly change functionality. I see this over and over again. Users don't read things they assume are static.

>We users simply don't expect that buttons will suddenly change functionality. I see this over and over again. Users don't read things they assume are static. Users navigate by item placement, rather than color/text/size/shape. This is interface design 101. On black Friday last year, I ordered a nice sheet set as a Christmas present for my SO, and the website was set up such that you could click through all the different colors and sizes for each sheet set and the same product page would simply update with Ajax to include new images/prices. So I found the sheets that I wanted and clicked "Add to Cart" -- the location of the button never changed, so I didn't really have to look at it in order to do this. I found out only much later that the "Add to Cart" button updated on a few of the sheet sets to include a small "Will ship on <date two months in the future>" message above it, indicating that they were out of stock. The button itself remained unchanged, and in the same position. The company was like "well, we warned you on the ordering page" I had to go back to the website to figure out what they were talking about. They ended up changing their policy of offering out of stock items for sale, in response to massive customer backlash. If they actually wanted to notify users, they could have grayed out the "Add to Cart" button and created a new "Reserve for <Date>" or "Pre-Order, ships <Date>" button in a different location (probably below the "Add to Cart"). ALWAYS assume users won't notice your message, unless you force them to do something different than what they're used to.