Welcome to the forum, Dr.Dale,
It is nice to know that you intend creating a website with Mathematical formulae;
The best way to do it is recall from memory or refer a standard textbook;
you may also add Theorems/Conjectures/Laws/Postulates and definitions and SI Units too, with pictures wherever required. Values of Scientific constants etc. may also be added.
I think HTML doesn't support certain symbols like pi, phi, theta etc. You would have to take the assistance of a professional webdesigner.
You may also use a search engine to get the desired information from the Net. Care should be taken not to reproduce verbatim as that may amount to Copyright infringement.
You may take the permission from the webmaster to put the information/pictures on your site. From experience, I can tell you that, often, permission is granted for placing a link on your site. In some cases, you may also be allowed to put the information mentioning the source.
However, as a precautionary measure, it is always safe to get prior permission.
The most difficult part is getting the hits. For that you would have to register with Search Engines, some of them provide free registration.