My solution to the quiz exercise (feedback requested)

// <- this is syntax for commenting, this code will not run.
//From now I'll communicate with comment.

//Questions
//This is just subjective thing about organizing code, 
//you don't have to care for change made to this.
//Also, I used only one var to group questions. This is okay but 
//generally not welcome in TreeHouse.
var question1 = prompt("What year did Columbus arrive in the Western Hemisphere?"),
    question2 = prompt("How many moons does Mars have?"),
    question3 = prompt("Fill in the blank: ____ Sagan, author of Cosmos."),
    question4 = prompt("Fill in the blank: Lake _____ is one of the Great Lakes."),
    question5 = prompt("Fill in the blank: Martin Luther King said \"I had a ______\".");

//Score counter
var score = 0;

//Grading
//Changed grader to ignore case-sensitivity to give some forgiveness.
if (parseInt(question1, 10) === 1492) { //parseInt(n, 10) makes sure it returns decimal.
  score += 1;
}

if (parseInt(question2, 10) === 2) {
  score += 1;
}

if (question3.toLowerCase() === "carl") { //toLowerCase() transforms text to lowercase.
  score += 1;
}

//You can either apply toLowerCase() to all case or
//just make this an exception and save it as variable.
//Also, I'd like to separate each comparison in groups of 1 or 2.
var answer = question4.toLowerCase();
if (answer === "michigan" || 
    answer === "erie" ||
    answer === "superior" || 
    answer === "huron" || 
    answer === "ontario") {
  score += 1;
}

if (question5.toLowerCase() === "dream") {
  score += 1;
}

//General feedback template
//Extracted common part of feedback to save up few typing and for future maintainability.
var feedback = "<p>Congratulations, you answered " + score + " questions correctly.";

//Give feedback
//4 indent space is preferred but I like to use 2.
if (score === 5) {
  document.write(feedback + 'You have earned a gold crown!</p>');
} else if (score >= 3) { //Changed this from score == 4 || score == 3
  document.write(feedback + 'You have earned a silver crown!</p>');
} else if (score >= 1) { //Changed this from score == 2 || score == 1
  document.write(feedback + 'You have earned a bronze crown!</p>');
} else {
  document.write("<p>You answered all questions incorrectly. Please go sit in the corner.</p>");
}