Hi,
In Odoo, A Website must linked to a company. there is no such option to handle a single website for multi company. If you are looking for third party module, you have to provide one company to handle the functionalities from the website like Quotation, SO, PO, e-commerce, etc.

If you are looking for a common website without any functionalities related to company operations you may customize it.

Finally, it is better to use without a customization in company website. Because it may chance to break your website functionalities entirely.

Regards