Edit Your error pages:
Insert a redirect to index.html or the other start page.
Visit dotcomxy.com/bubu to see a working example.
When You see how it works, modify error pages.
Copy these lines and paste in blank error pages.
Modify as You like.
It works for all my 218 websites.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8">
<title>Error Page ... You did something wrong?</title>
<meta http-equiv="REFRESH" content="3;URL=http://www.sciii.com">
</head>
<body dir="ltr" style="background-color: rgb(192, 192, 192);"
lang="nl-NL">
<p><font color="
#4c4c4c"><font style="font-size: 96pt;" size="7"><i>Hello!</i></font></font></p>
<p><font color="
#4c4c4c"><font style="font-size: 96pt;" size="7"><i>Goodbye
...</i></font></font></p>
<p><br>
<br>
</p>
</body>
</html>