Pretty bad I must say. Not only the design looks horrible, but the script is bugged also.
For example:
Link: https://bitplanet.online/login
You can send data like this using POST Method: 12345'"\'\");|]*{%0d%0a<%00>%bf%27'?#?#
You will get the following Error:
This can be manipulated into disclosing sensitive information.
You can also notice, this is using a Vulnerable Jquery version (1.9.2): https://bitplanet.online/phpmyadmin/js/jquery/jquery-ui-1.9.2.custom.min.js
This is vulnerable not only to XSS Attacks, but can also disclose sensitive information.
More information about this specific vulnerability: https://zerobitsecurity.wordpress.com/2015/11/15/xss-vulnerability-on-_attachdatepicker-function-in-jquery-ui-1-9-2/