Popup in javascript 7/8

clicks on a link, a new window opens and displays a page.

There are two ways to do this. You can add a TARGET="_blank" to the <a>-tag, but this simply opens a new browser window that completely obscures the old one.

This may be what you want, but at other times a small window on top of the large browser window is much better. This small window is popularly known as apopup.

First the basic syntax of how to create a popup, then an explanation of the script, including a table of the most common arguments you can give to a popup and the problem of focusing.
Then a new way of adding popup behavior to a link. This site uses the new system because it's much cleaner than the old one.
Finally some notes about writing content directly into the popup. This gives several problems, most importantly the confusion over exactly what the URL of the popup is.

Name	Code
Alert box	<!DOCTYPE html> <html> <head> <script> function myFunction() { alert("Hello! I am an alert box!"); } </script> </head> < body> <input type="button" onClick="myFunction()" value="Show alert box" /> </body> </html>
Confirm box	<p>Click the button to display a confirm box.</p> <button onClick="myFunction()">Try it</button> <p id="demo"></p> <script> function myFunction() { var x; var r=confirm("Press a button!"); if (r==true) { x="You pressed OK!"; } else { x="You pressed Cancel!"; } document.getElementById("demo").innerHTML=x; } </script> </body> </html>
Prompt box	<!DOCTYPE html> <html> <body> <p>Click the button to demonstrate the prompt box.</p> <button onClick="myFunction()">Try it</button> <p id="demo"></p> <script> function myFunction() { var x; var name=prompt("Please enter your name","Harry Potter"); if (name!=null) { x="Hello " + name + "! How are you today?"; document.getElementById("demo").innerHTML=x; } } </script> </body> </html>