How to Put a Popup Message on Your Websiteby Shawn Farner
Open the HTML file for your Web page in Notepad, the text application bundled with Windows.
Copy and paste the following code into your HTML file between theand tags:
Replace the "Insert your message here" text between the quotation marks with the message you want visitors to see when they get to your page.
Click "File," then click "Save" to save your changes. When you publish your updated page to the Web and visit in your Web browser, you'll be greeted with a popup message box containing the text you added.