1. Start by finding the “plugins” folder which is located below the “fckeditor/editor” folder.
2. Create a new folder, name it “openurl”.
3. Add an icon within the “openurl” folder, name it “openurl.gif”.
4. Create a new file within the “openurl” folder, name it “fckplugin.js”, and add the following code:

// Our method which is called during initialization of the toolbar.
function OpenUrl()
{
}

// Disable button toggling.
OpenUrl.prototype.GetState = function()
{
	return FCK_TRISTATE_OFF;
}

// Our method which is called on button click.
OpenUrl.prototype.Execute = function()
{
	window.open('http://www.kindblad.com');
}

// Register the command.
FCKCommands.RegisterCommand('openurl', new OpenUrl());

// Add the button.
var item = new FCKToolbarButton('openurl', 'Open URL');
item.IconPath = FCKPlugins.Items['openurl'].Path + 'openurl.gif';
FCKToolbarItems.RegisterItem('openurl', item);

5. Now we need to define where we want our button to be shown in the toolbar. Open up “fckeditor/fckconfig.js” and look for:

FCKConfig.ToolbarSets["Default"] = [
	['Source'],
	['Cut','Copy','Paste','PasteText','PasteWord','-','SpellCheck'],
	...

Add ‘openurl’ anywhere in the toolbar definition, e.g.:

FCKConfig.ToolbarSets["Default"] = [
	['openurl,'Source'],
	['Cut','Copy','Paste','PasteText','PasteWord','-','SpellCheck'],
	...

6. And lastly, we need to tell FCKeditor to load our plugin, we do this by finding the following string in the “fckeditor/fckconfig.js”.

FCKConfig.PluginsPath = FCKConfig.BasePath + 'plugins/' ;

Add the following code below the line above:

FCKConfig.Plugins.Add('openurl');

That’s it.