What is Noframes tag?

Is it very important tag like H1, h2, or not? Please tell me how important of this keyword regarding SEO?

Noframes is what you use to give the browser some info for browsers that don't support frames (which isn't many these days). Read: http://www.w3schools.com/tags/tag_noframes.asp

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It's useful because it gives you a way to stuff keyword content into a page with frames, but not nearly as important as header tags etc. You shouldn't really be using frames these days anyway.