A domain must be unique (for example there can only be one single Yahoo.com) and must be registered with a domain registrar (ie. NameCheap); while for sub domains, users can freely add it on top of the existing domain as long as their web host provide the service. Some would say sub-domains are the ‘third level’ domains in the sense that they are simply “sub folders” under the domain root directory, normally used to organize your website content in different languages or different categories.
^ March 16, 1992 memo from Mariam Leder, NSF Assistant General Counsel to Steven Wolff, Division Director, NSF DNCRI (included at page 128 of Management of NSFNET, a transcript of the March 12, 1992 hearing before the Subcommittee on Science of the Committee on Science, Space, and Technology, U.S. House of Representatives, One Hundred Second Congress, Second Session, Hon. Rick Boucher, subcommittee chairman, presiding)
Registries and registrars usually charge an annual fee for the service of delegating a domain name to a user and providing a default set of name servers. Often, this transaction is termed a sale or lease of the domain name, and the registrant may sometimes be called an "owner", but no such legal relationship is actually associated with the transaction, only the exclusive right to use the domain name. More correctly, authorized users are known as "registrants" or as "domain holders".
Many people may not know that a domain name can be registered at very reasonable prices, sometimes for as little as $.99 per year. In fact, the relatively low cost of domain name registrations can help businesses to register multiple domain names and build a domain name portfolio for use in promotional or brand-protection strategies. The key is to align your brand and relevant keywords to maximize the value your domain name can bring to your existing and future online presence.

An SSL certificate ensures all information transmitted to and from your website is protected from third parties attempting to access it. It is important because browsers, like Google Chrome, mark pages without https and the green padlock in the address bar as not secure. This can have a negative effect on the trustworthiness of your website. Pages that are protected with SSL receive better search engine rankings, and are more likely to be trusted by visitors.
When a website has been secured with an SSL certificate, a visitor will see a padlock icon in their web browser and they’ll be connected to the site using the https:// protocol. With the SSL certificate in place and the user accessing the site through https, the connection between the browser and the web server has been secured and sensitive information can safely be transferred.
Almost all the services offer some sort of page builder that makes it easy to drag and drop to build your page. These are great for getting started, but they often lock you into the service. Most page builders are proprietary to the service, or don't create HTML that's portable enough to be easily moved to another service if you decide it's necessary.
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