It is possible that some website stil using iframe elements in his website such as Google Doc. However, there is a solution to fix this problem. This by changing the Firefox engine in the Firefox Chrome extension Options page, from "web CSS Firefox" (stylsheet) to the "built-in browser Firefox" engine.
Just follow the steps here below to change the Firefox engine:
1. Install the Firefox Microsoft Edge extension back in your Microsoft Edge web browser
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2. First, click right on the Z icon in your browser toolbar
3. Select from the context menu the item "Options"
4. You see the Firefox Chrome extension Options page show up
5. Scroll a bit down until you see the topic "Firefox Engine", and enable the first radio button
6. And at last restart your web browser
What is the different from CSS and built-in Firefox? The CSS Firefox is more smoother in Firefoxing in and out of a web page.