Barebones client-side speed-reading application

<html>
<script>
//Author:  Jordan Stefanelli
//GPL License: Just kidding.  I don't care, this code is awful.

// Some global vars that the functions reference.
var g_content = '';     // content = array of split up words from the text area
var g_idx = 0;          // the current word to display (the #'d position of the word)
var g_interval = 400;   // How many milliseconds to update the word display
var g_running = false;  // Track if the application is running
var g_timer = null;     // Storage variable for the looping call to update & display words.

//  Gate-keeper to only allow starting if we're not running.
//  Called when clicking "start"
function start_words()
    {
    if (!g_running)
        {
        g_running = true;
        g_timer = setInterval(flash_words, g_interval);
        }
    }

//  Stop the looping call, reset the paragraph position to 0, signal that we are not running.
//  Called when clicking 'stop'
function stop_words()
    {
    if (g_running)
        {
        g_running = false;
        g_idx = 0;
        clearInterval(g_timer);
        }
    }

// This is called if you
function set_reading_interval()
    {
    g_interval = document.getElementsByName('display_interval')[0].value;
    update_reading_interval();
    }

// Called when clicking away from updating the reading interval box
function update_reading_interval()
    {
    if (g_running)
        {
        clearInterval(g_timer);
        g_running = false;
        start_words();
        }
    }

// This is called after you click away from the text box containing your reading content.
function getContent()
    {
    text = document.getElementsByName('content')[0].value;
    g_content = text.split(' ');
    }

// This method is internally called to update the word display.
function flash_words()
    {
    word = g_content[g_idx];
    document.getElementsByName('display_field')[0].value = word;
    g_idx = ( g_idx + 1 ) % g_content.length;
    }

</script>
<body>
<textarea name="display_interval" onBlur="set_reading_interval();">400</textarea>
<textarea name="content" style="width:400px;height:400px;" onBlur="getContent();"></textarea>
<br>
<textarea style="font-size:200px;font-family:courier new;" name="display_field">test</textarea>
<br>
<input type="button" value="Go." onClick="start_words();flash_words();"></input>
<input type="button" value="Stop." onClick="stop_words();"></input>
</body>
</html>