Memory Game using JavaScript

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <style type="text/css">
        .mainboardClass
        {
            margin:0px auto;
            width:800px;
            height:540px;
            background-color:#ccc;
            padding:24px;
            border:dashed;


        }
        div#minboard>div {
            background: url(Images/Untitled123.png) no-repeat;
             margin: 0px auto;
            text-align: center;
            margin: 10px;
            padding: 20px;
            width: 71px;
            height: 71px;
            cursor: pointer;
            text-align: center;
            border: thin;
            float:left;
            font:24px;
        }
    </style>
    <script type="text/javascript">
        //Fisher Yates Shuffle Algorithm
        var arr = ['A','A','B','B','C','C','D','D','E','E','F','F','G','G','H','H','I','I'];
        var memory_values_array = [];
        var memory_values_id = [];
        var tilesFliped = 0;
        Array.prototype.shuffle = function () {
            var i = arr.length, j, temp;
            while (--i > 0) {
                j = Math.floor(Math.random() * (i + 1));
                temp = this[j];
                this[j] = this[i];
                this[i] = temp;
            }
        }

        function newboard() {
            var adddivs = '';
            arr.shuffle();
            for (var i = 0; i < arr.length; i++) {
                //Adds div dynamically to the array lenth
               adddivs += '<div id="title_' + i + '"  onclick=" pageflip(this, \''+arr[i]+'\'); "></div>';
            }
            document.getElementById('minboard').innerHTML = adddivs;
        }

        function pageflip(ids,tileValue)
        {
            //Check the tile is empty
            if(ids.innerHTML=="" && tileValue.length < 2)
            {
                ids.style.color = '#FFF';
                //Assign the value to the tile
                ids.innerHTML = tileValue;
                ids.style.background = 'URL() no-repeat';
                //push the first tile value into the array
                if (memory_values_array.length == 0) {
                    memory_values_array.push(tileValue);
                    memory_values_id.push(ids.id);
                }
                    //If 2nd tile is clicked
               else if (memory_values_array.length == 1 )
               {
                   //Push the value in "memory_values_array"
                   //Push the dive in "memory_values_id"
                    memory_values_array.push(tileValue);
                    memory_values_id.push(ids.id);

                   //if both values selected matches then
                    if(memory_values_array[0]==memory_values_array[1])
                    {

                        tilesFliped = tilesFliped + 2;
                        memory_values_array=[];
                        memory_values_id = [];

                        //New board is generated if all tiles are successfully mapped
                        if(tilesFliped==arr.length)
                        {
                            clearTimeout(timer);
                            alert("Board Cleared Take this as Bonus");
                            newboard();
                        }
                    }
                    else {
                        //If both clicked tiles does not match then Empty the array
                        //Change the back ground color of the tiles
                        function ifNothingMatches() {
                            var id1 = document.getElementById(memory_values_id[0])
                            var id2 = document.getElementById(memory_values_id[1])
                            id1.innerHTML = "";
                            id1.style.background = 'URL(Images/Untitled123.png) no-repeat';
                            id2.innerHTML = "";
                            id2.style.background = 'URL(Images/Untitled123.png) no-repeat';
                            memory_values_array = [];
                            memory_values_id = [];
                        }
                        setTimeout(ifNothingMatches,700)
                    }
                }
            }
        }
    </script>

</head>
<body>
    <div id="minboard" class="mainboardClass"></div>
    <script>newboard();
    </script>
 </body>
</html>