Frozen Row

You can embed a spreadsheet so that no pop-out icon shows.

<iframe height="500" src="https://docs.google.com/spreadsheets/d/SPREADSHEET ID/edit?usp=sharing&embedded=true&rm=demo" width="75%"></iframe>

With this method the frozen rows stay frozen when the viewer scrolls the sheet.

A side effect of this method is that the page automatically scrolls down to the document area.

Idea posted by ChiefChippy2 here