Can't save default page's html in cwp.

Hi,
When I tried to edit the default HTML page used when a domain is created through the admin panel, I went to the option User Accounts ---> Features,Themes,Languages ---> Template Editor Pages. Then, when I paste my HTML and click save, it doesn't save my HTML fully; instead, it just saves the first 6 lines.

May I know where this HTML lie in the file manager so I can edit and save it there manually?

Default page:
https://wiki.centos-webpanel.com/how-to-change-default-website
/usr/local/apache/htdocs/index.html

Account templates:
https://wiki.centos-webpanel.com/custom-account-templates

Thanks mate.