Popup div over 'article' tag takes on the styles of the article, which I don't want.

Suppose I have a article inside an article tag. The article sometimes has its own CSS style declarations.
I also have DIV that pops up over the article. It is defined in the html before the article tag is encountered, but is moved above it by JavaScript. In Microsoft Edge (I did not test elsewhere), I find that the styles in the article are applied to the DIV. This is not good!
For instance, the popup DIV has a textarea that the user is supposed to enter an opinion into. Unfortunately sometimes that textarea is very small, due to a style that occurred in the main article.

I could make specific classes for the textarea, and for other elements in the popup, but its hard to anticipate every possible style that might appear in the article tag, and which have to be counter-acted.

Is there a solution to this? Can I prevent inheritance?