I wouldn't be so sure. It can happen. That's the thing with randomness, it doesn't mean "fairly even distribution across a range", it means "totally unpredictable"

http://dilbert.com/strips/comic/2001-10-25/

However, I'd be looking at your code - what does it look like? Also, what kind of device were you running it on - these can be factors too.

There are some examples on the Mozilla Developer Network page:

/**
 * Returns a random number between min (inclusive) and max (exclusive)
 */
function getRandomArbitrary(min, max) {
    return Math.random() * (max - min) + min;
}

/**
 * Returns a random integer between min (inclusive) and max (inclusive).
 * The value is no lower than min (or the next integer greater than min
 * if min isn't an integer) and no greater than max (or the next integer
 * lower than max if max isn't an integer).
 * Using Math.round() will give you a non-uniform distribution!
 */
function getRandomInt(min, max) {
    min = Math.ceil(min);
    max = Math.floor(max);
    return Math.floor(Math.random() * (max - min + 1)) + min;
}

Here's the logic behind it. It's a simple rule of three:

Math.random() returns a Number between 0 (inclusive) and 1 (exclusive). So we have an interval like this:

[0 .................................... 1)

Now, we'd like a number between min (inclusive) and max (exclusive):

[0 .................................... 1)
[min .................................. max)

We can use the Math.random to get the correspondent in the [min, max) interval. But, first we should factor a little bit the problem by subtracting min from the second interval:

[0 .................................... 1)
[min - min ............................ max - min)

This gives:

[0 .................................... 1)
[0 .................................... max - min)

We may now apply Math.random and then calculate the correspondent. Let's choose a random number:

                Math.random()
                    |
[0 .................................... 1)
[0 .................................... max - min)
                    |
                    x (what we need)

So, in order to find x, we would do:

x = Math.random() * (max - min);

Don't forget to add min back, so that we get a number in the [min, max) interval:

x = Math.random() * (max - min) + min;

That was the first function from MDN. The second one, returns an integer between min and max, both inclusive.

Now for getting integers, you could use round, ceil or floor.

You could use Math.round(Math.random() * (max - min)) + min, this however gives a non-even distribution. Both, min and max only have approximately half the chance to roll:

min...min+0.5...min+1...min+1.5   ...    max-0.5....max
└───┬───┘└────────┬───────┘└───── ... ─────┘└───┬──┘   ← Math.round()
   min          min+1                          max

With max excluded from the interval, it has an even less chance to roll than min.

With Math.floor(Math.random() * (max - min +1)) + min you have a perfectly even distribution.

 min...  min+1...    ...      max-1... max....   (max+1 is excluded from interval)
└───┬───┘└───┬───┘└─── ... ┘└───┬───┘└───┬───┘   ← Math.floor()
   min     min+1               max-1    max

You can't use ceil() and -1 in that equation because max now had a slightly less chance to roll, but you can roll the (unwanted) min-1 result too.

The random number function is an equation that simulates being random, but, it is still a function. If you give it the same seed the first answer will be the same.

You could try changing the seed, and do this when the javascript is first loaded, so that if there is a time component to the random number generator, then it can use the delays of pages being loaded to randomize the numbers more.

But, you may want to change the seed. You can use the Date() function, then get the milliseconds and use that as the seed, and that may help to scramble it up first.

My thought that there is a time component to the generator is the fact that it changes with an alert, as that will delay when the next number is generated, though I haven't tested this out.

UPDATE:

I realize the specification states that there is no parameter for Math.random, but there is a seed being used.

I came at this from C and then Java, so the fact that there was no error using an argument led me to think it used it, but now I see that that was incorrect.

If you really need a seed, your best bet is to write a random number generator, and then Knuth books are the best starting point for that.