how to solve 404 error ?

[SanGoku]

Redirect the 404 error somewhere else. If people are reaching /specials, which is an error page, you can tell your server to redirect people fto /special instead.

Correct the source link. If the broken link sending traffic to the not found error page exists on your website, and is under your control, you can correct the broken link at the source. However, most 404's come from sources you don't control.

Restore deleted pages. Sometimes, you delete pages from your website and people still come to your website to find those page you deleted. If somebody tries to find a deleted page, they'll get a 404 error. To fix this, you can usually restore the deleted page.

Ignore the not found error. Sometimes, for low priority not found errors that aren't costing you customers, you can simply ignore the 404 is an acceptable solution.