<p>Sometimes software installers force you to scroll to the end of the EULA before the “I agree” box is enabled.  How can I produce the same effect on a web page?</p>

```
```
<html>
    <head>
        <script type="text/javascript">
            function setupPage() {
                var agreement = document.getElementById("agreetext");
                var visibleHeight = agreement.clientHeight;
                var scrollableHeight = agreement.scrollHeight;
                if (scrollableHeight > visibleHeight) {
                    var checkbox = document.getElementById("agreebox");
                    checkbox.checked=false;
                    checkbox.disabled=true;
                    agreement.onscroll = handleScroll;
                }
            }

            function handleScroll() {
                var agreement = document.getElementById("agreetext");
                var visibleHeight = agreement.clientHeight;
                var scrollableHeight = agreement.scrollHeight;
                var position = agreement.scrollTop;
                if (position + visibleHeight == scrollableHeight) {
                    document.getElementById("agreebox").disabled=false;
                }
            }
        </script>
    </head>
    <body>
        <form>
            <textarea id="agreetext" rows="8" cols="40">Long agreement</textarea>
            <br/><br/>
            <input type="checkbox" id="agreebox" value="true"/> <label id="agreelabel" for="agreebox">I agree</label>
            <br/><br/>
            <input type="submit" value="Continue"/>
        </form>
        <script type="text/javascript">
            // We put this at the end of the page rather than in an document.onload
            // because the document.onload event doesn't fire until all images have loaded.
            setupPage();
        </script>
    </body>
</html>
```
```