I made lemon curd and left it on the counter for three hours accidental while we went to a movie. Should I toss it?

The eggs are cooked in the curd. There should be no problems being left out for that short a time.

We serve breakfast pastries that I've made containing lemon curd (albeit, baked) which sit on a buffet for 4 hours. I suspect you're fine. What movie did you see?

Well lemons have a pH of 2, and most microorganisms won't grow below a pH of 4.6. After three hours I'd think it'd still be good to use, just be sure to refrigerate it afterwards just to be extra safe.

I wouldn't toss it, but my system is used to raw eggs, street food in foreign countries and who knows what else. Your decision and yours only.

I wouldn't.