These days, it often happens that you find “Error 404” on web pages, which means the specified resource is not available on that server. There can be many different reasons such as broken links, wrong URLs, or pages that have been deleted.
404 errors can be really annoying to the users but, this being said, they are part and parcel of the life of the web. Website owners should endeavour and minimise the number of 404 errors, maybe by checking broken links regularly, or establishing an assigned redirection whenever content is moved or deleted.
A good 404 could also optimise visitor experience by offering extra services or alternative pages that he can view. You cannot, yet, avoid the 404 errors. The only way-out is to minimise the number at a time.