The following script shows an image "correct.gif" or "incoorect.gif" according to the given answer.
When clicking the "clear"-button it erases the words of the feedback but not the image.
I thought I could add document.getElementById('img').src = 'empty.gif'; to the cleartext function while refering to this function from the "clear"-button. It erases the text, but doesn't change the image with the empty.gif image. Maybe a stupid question, but I'm an absolute newbie and am just learning.

Code:
var question1 = '<strong>Who</strong>.................?';
var choice1 = 'Mr. Johnson.';
var choice2 = 'In 1875.';
var choice3 = '78 years old.';
var choice4 = 'In 1949.';
var correctAnswer = 1;   // Indicate the best answer with this variable.

function check(input,x) {
    if (x==0) {
    alert("You didn't choose an answer");
    } else {
    if (x==correctAnswer) {
           input.result.value = "Excellent! When the question starts with `WHO` your answer should be a name or describe someone.";
        document.getElementById('img').src = 'correct.gif';
        } else {
        input.result.value = "This answer is incorrect. The answer on a 'WHO' question can't be a time expression or age.";
        document.getElementById('img').src = 'incorrect.gif';
        }
}
}

function cleartext(input) {
        input.result.value = ''; // Clear text field.
        document.getElementById('img').src = 'empty.gif';
}

// Initialize answer to 0 to trap no selection.
answer=0;

// Generate the HTML code for the top of the web page.
document.write('<HR>');
document.write(question1);

// Generate the HTML code for the radio button choices.

document.write('<FORM NAME="questn1" id="form_questions">');
document.write('<OL">');
document.write('<LI><input type="radio" name="answera" onClick="answer=1">',choice1);
document.write('<LI><input type="radio" name="answera" onClick="answer=2">',choice2);
document.write('<LI><input type="radio" name="answera" onClick="answer=3">',choice3);
document.write('<LI><input type="radio" name="answera" onClick="answer=4">',choice4);
document.write('</OL>');

// Generate the HTML code for the buttons and response text area.
document.write('<HR>');
document.write('<INPUT TYPE="button" VALUE="Check Answer" onClick="check(this.form,answer)"> ');
document.write('<INPUT TYPE="reset" VALUE="  Clear  " onClick="cleartext(input)"> ');
document.write('<img src="empty.gif" id="img" /> <br/> ');
document.write('<INPUT TYPE="text" NAME="result" SIZE="100" class="style55" > <br/> ');
document.write('</FORM>');


cleartext(document.questn1);     // Clear text field on reload.