Any web site disabling the ability to “paste” a password from the clipboard is a web site not deserving of anyone’s patronage because they show they lack even the most basic cyber security knowledge, not to mention the customer unfriendliness of such an act:

You know that. But what’s crazy is that, in 2015, some websites are intentionally disabling a feature that would allow you to use stronger passwords more easily—and many are doing so because they wrongly argue it makes you safer.

Here’s the problem: Some sites won’t let you paste passwords into login screens, forcing you, instead, to type the passwords out. This makes it impossible to use certain kinds of password managers that are one of the best lines of defense for keeping accounts locked down.

Typically, a password manager will generate a long, complex, and—most importantly—unique password, and then store it in an encrypted fashion on either your computer or a remote service. All you have to do is remember one password to enter all of your others. In essence, the task of remembering dozens of passwords is relegated to the manager, meaning that you don’t have to deploy that same, easy to remember password on multiple sites.