Is it healthy to eat salad at every meal?

Sure, as long as you're also getting enough of all the macro nutrients (good proteins, carbs and fats) and not loading it up with junk like you might get from fast food places or salad bars. You almost can't have too many high fiber foods from veggies. Personally, I'd be bored after a while of having salad with every meal - for me, one healthy salad a day is plenty. Goes great with grilled fish or chicken and olive oil and vinegar.