How to control spacing in error messages?

I’ve modified the CSS in my forms to have the field labels in the left 50% and the input boxes in the right 50% and it all works well. I’ve also controlled the spacing between the lines using CSS.

But how do I control/modify the spacing that appears when there’s an error message? i.e. if the user misses a required field the error message that appears pushes all the input boxes down considerably and the bottom of the form (and the send button) go below the fold. I’d like to have those message show up more discreetly or at least not push everything down so much (multi-line gap).

Where and how do I control the spacing / line height etc., of these error messages? What code do I need?

TIA.

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