I am getting HTTP Error 404.20 - Not Found for the below Url. Whereas the expectation is to display any custom Error page .
https://localhost/mysite/dataw/yyyyy/%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E%3Cscript%3Ealert%281%29%3C%2fscript%3E
404.20 error means Too Many URL Segments
, I found that the URL requested in your screenshot is too long, you can specify the maximum number of segments permitted in a URL through the maxurlSegments property.