any negative effect cause by 404 error to SEO?

Broken Links like this are not liked by search engine robot. A webpage showing this type of error may lose faith by Search engine.

And what about if you set a page by help of htacess means in case of 404 error a page display always with some contents like "Search another keywords or oh sorry page was removed so please check homepage" We can redirect also to any active page of website for 404 erros. Then how search engine's bots will view our pages?

It think this types of problem with about all big websites in search or other things but they set a page for 404 errors.

I think if you set a page for this error then all problem can be sort out.

Thanks

Yes, it is a crawler error and Google will even report it in the Webmaster Tools section.

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