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  1. What is a Parked Domain?

Similarly to an Addon Domain, you can add your own domain name to your account using the Parked Domains section. But instead of creating a new website folder for the domain, you can select an existing domain to “park” your new domain on. By doing so, both domains will serve the same website.

However, note that Parked Domains simply mean that the domains both serve content from the same directory. With a simple HTML website or very basic PHP site, the same website will be shown on both domains. However, when using a more complex script or CMS, the results may vary. For example, WordPress always redirects visitors to the Website URL configured in the WordPress settings, so the parked domains will be redirected to the original domain.

So by default, Parked Domains will show the same website, but the actual results may differ depending on the content you’re hosting on the site your domain is parked on.

Hotlinking and embedding images and other (static) files on other websites is blocked.

so all resources (JS, CSS, etc.) that do not belong to the current domain are blocked,
that’s why your website appearance is broken.

In addition, all links, like this one for login lead to the “old” address - so again there is no point in keeping it.

It would be best if you choose only one of those two addresses that you will use
and then upload the whole complete website there + DB.

And that would also be good in terms of SEO so that for example Google does not offer results for two domains in SERP.