Our teacher thought us concept of counter resonance that it is very unstable (its resonance when 2 different electron density region trying to get stabalised from same pi bond of vacant orbital or something so they counter each other and thats very unstable)
But then HNO3 has equivalent resonance but NO3- also has counter resonance so is not HNO3 should have higher resonance energy
Also one more dbt why does HNO3 dont have intra H bond