Site pinning IE9 considerations

Thumbnail Buttons

1. Buttons persists between pages. So when you navigate to a page which doesn't support the button click event the button functionality becomes redundant and you need to first remove any buttons.
2. If the page is minified then you probably also want the button control to maximise the window.
3. Buttons can only be created once (see http://msdn.microsoft.com/en-us/library/ff976319(v=VS.85).aspx), but you can change the icon's and hide the buttons. So define four buttons before saving them, then change/hide as needed by sections of the app. 

Jumplist

1. When adding items to the jumplist there is no way to interrogate it to find out what you've already added.
2. If you have two distinct areas of your site which have their own JumpList e.g. "Mens" + "Womens" then you should always check what the page was pinned under, in case your users stray over to the other section and wonder why cross dressing is being promoted.
3. There may be many tabs opened and they all are editing the jumplist they need to be aware of the other.
4. If you store what is being added to the Jumplist and use this to determine whether to add an item. Beaware users can manually remove them.

Overlays

1. If you have multiple overlays then, say you have paused a video and received a message from someone on the page. Then your overlay will be the icon added last. In such circumstance you should consider rotating the overlays