There are two main ways of opening a page in a new window from a link.
The HTML way involves the <a href> tag using the target attribute. The value of the target attribute can either be a browser-reserved window name, or an alphanumeric name.
The main browser-reserved name in use is _blank, our example:
<a href="mynewpage.html" target="_blank">My New Page</a>
Will open mynewpage.html in a brand new window.
If you click this link again (while keeping the new window open), it opens another new window. And another. And another.
If we want to keep things cleaner by only opening a new window if one isn't already there then make up a window name (don't start the name with an underscore, else the browser thinks its one of its special windows) and use that:
<a href="mynewpage.html" target="thisismywindow">My New Page</a>
Now click our link lots of times, only one page should open.
Now an example piece of code: