Use Embed Gadget

Some codes will work by embedding them in the Embed Gadget thus making it unnecessary to create your own gadget .

Insert>>More Gadgets>>Featured. Look for embed gadget and add it to your page.
Paste your code for your form or whatever in the gadget. Set the size for 100 percent wide and 800 pixels high (modify as needed).
Scroll down in the setup and select Include a scrollbar on gadget when necessary (optional) .
Click OK and save your page.

Example Code:
<iframe id="forecast_embed" type="text/html" frameborder="0" height="245" width="100%" src="https://forecast.io/embed/#lat=43.015082&lon=-84.175271&name= Owosso Michigan"> </iframe>

Result: