Redirect 404 error pages to home page in Blogger

copy it and paste code  in your custom page not found field (settings >> search preferences >> custom page not found)

<h1>Oops 404!</h1>

<br><b>The page you are looking for may have been renamed or does not exist in this server.</b>

<br><br><b>You will be redirected to homepage shortly.</b>

<script>

blogger_redirect = setTimeout(function() { location.pathname= "/" }, 7000);

</script>

7000 is 7 seconds. Change it if you want