Reasons not to use iframes?
I've heard a lot of times that it's a bad idea to use iframes. But I never knew why. Is it really a bad idea? Could someone list a number of resons not to use them?

Supposing I wanted to use an iframe to load some content asynchronously to load my site faster, if this content wasn't meant to be indexed by search engines. Is it still bad idea to use an iframe?
Reasons not to use iframes?
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I've heard a lot of times that it's a bad idea to use iframes. But I never knew why. Is it really a bad idea? Could someone list a number of resons not to use them?

Supposing I wanted to use an iframe to load some content asynchronously to load my site faster, if this content wasn't meant to be indexed by search engines. Is it still bad idea to use an iframe?