In Atlassian Confluence you can develop custom Macro or Gadget. What is the difference between these two? From what I have seen: "Gadgets are generated by scripts that run entirely in the user's web browser, not on the Confluence server" What are the implications of it?
IMU gadget may stop working when your company's firewall blocks access to its provider, as soon as it's hosted outside of the corporate WAN perimeter; macroses won't stop as they're hosted on the Condluence server which is inside your company's perimeter.
Not applicable for On-Demand instances, though.