Do you remember the game of finding correct words in a table? This is the effect used here to build a 404 not found page. Besides, there is search box for the visitors to look for what they want really. Also there exist navigation buttons to guide users to the main pages pf the site.


HTML
<!-- This script got from www.devanswer.com  -->
<div id="wrap">
<div id="wordsearch">
<ul>
<li>k</li>
<li>v</li>
<li>n</li>
<li>z</li>
<li>i</li>
<li>x</li>
<li>m</li>
<li>e</li>
<li>t</li>
<li>a</li>
<li>x</li>
<li>l</li>
<li class="one">4</li>
<li class="two">0</li>
<li class="three">4</li>
<li>y</li>
<li>y</li>
<li>w</li>
<li>v</li>
<li>b</li>
<li>o</li>
<li>q</li>
<li>d</li>
<li>y</li>
<li>p</li>
<li>a</li>
<li class="four">p</li>
<li class="five">a</li>
<li class="six">g</li>
<li class="seven">e</li>
<li>v</li>
<li>j</li>
<li>a</li>
<li class="eight">n</li>
<li class="nine">o</li>
<li class="ten">t</li>
<li>s</li>
<li>c</li>
<li>e</li>
<li>w</li>
<li>v</li>
<li>x</li>
<li>e</li>
<li>p</li>
<li>c</li>
<li>f</li>
<li>h</li>
<li>q</li>
<li>e</li>
<li class="eleven">f</li>
<li class="twelve">o</li>
<li class="thirteen">u</li>
<li class="fourteen">n</li>
<li class="fifteen">d</li>
<li>s</li>
<li>w</li>
<li>q</li>
<li>v</li>
<li>o</li>
<li>s</li>
<li>m</li>
<li>v</li>
<li>f</li>
<li>u</li>
</ul>
</div>
<div id="main-content">
<h1>We couldn't find what you were looking for.</h1>
<p>Unfortunately the page you were looking for could not be found. It may be
temporarily unavailable, moved or no longer exist.</p>
<p>Check the URL you entered for any mistakes and try again. Alternatively, search
for whatever is missing or take a look around the rest of our site.</p>
<div id="search">
<form>
<input type="text" placeholder="Search" />
</form>
</div>
<div id="navigation">
<a class="navigation" href="">Home</a><a class="navigation" href="">About
Us</a>
<a class="navigation" href="">Site Map</a>
<a class="navigation" href="">Contact</a>
</div>
</div>
</div>

<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js'></script><div id="bcl"><a style="font-size:8pt;text-decoration:none;" href="http://www.devanswer.com ">Developers Answer</a></div>
                        

CSS
@import url(https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,300);

body {
	background-color: #335B67;
	background: -ms-radial-gradient(ellipse at center,  #335B67 0%, #2C3E50 100%) fixed no-repeat;
	background: -moz-radial-gradient(ellipse at center,  #335B67 0%, #2C3E50 100%) fixed no-repeat;
	background: -o-radial-gradient(ellipse at center, #335B67 0%, #2C3E50 100%) fixed no-repeat;
	background: -webkit-gradient(radial, center center, 0, center center, 497, color-stop(0, #335B67), color-stop(1, #2C3E50));
	background: -webkit-radial-gradient(ellipse at center,  #335B67 0%, #2C3E50 100%) fixed no-repeat;
	background: radial-gradient(ellipse at center, #335B67 0%, #2C3E50 100%) fixed no-repeat;
	font-family: 'Source Sans Pro', sans-serif;
	-webkit-font-smoothing: antialiased;
	margin: 0px;
}

::selection {
	background-color: rgba(0,0,0,0.2);
}

::-moz-selection {
	background-color: rgba(0,0,0,0.2);
}
	

a {
	color: white;
	text-decoration: none;
	border-bottom: 1px solid rgba(255,255,255,0.5);
	transition: all 0.5s ease;
	-moz-transition: all 0.5s ease;
	-o-transition: all 0.5s ease;
	-webkit-transition: all 0.5s ease;
	margin-right: 10px;
}

a:last-child { margin-right: 0px; }

a:hover {
	text-shadow: 0px 0px 1px rgba(255,255,255,.5);
	border-bottom: 1px solid rgba(255,255,255,1);
}

#noscript-warning {
	width: 100%;
	text-align: center;
	background-color: rgba(0,0,0,0.2);
	font-weight: 300;
	color: white;
	padding-top: 10px;
	padding-bottom: 10px;
}



/* === WRAP === */

#wrap {
	width: 80%;
	max-width: 1400px;
	margin:0 auto;
	height: auto;
	position: relative;
	margin-top: 8%;
}



/* === MAIN TEXT CONTENT === */

#main-content {
	float: right;
	max-width: 45%;
	color: white;
	font-weight: 300;
	font-size: 18px;
	padding-bottom: 40px;
	line-height: 28px;
}

#main-content h1 {
	margin: 0px;
	font-weight: 400;
	font-size: 42px;
	margin-bottom: 40px;
	line-height: normal;
}



/* === NAVIGATION BUTTONS === */

#navigation { margin-top: 2%; }

#navigation a.navigation {
	display: block;
	float: left;
	background-color: rgba(0,0,0,0.2);
	padding-left: 15px;
	padding-right: 15px;
	color: white;
	height: 41px;
	line-height: 41px;
	text-decoration: none;
	font-size: 16px;
	transition: all 0.5s ease;
	-moz-transition: all 0.5s ease;
	-o-transition: all 0.5s ease;
	-webkit-transition: all 0.5s ease;
	margin-right: 2%;
	margin-bottom: 2%;
	border-bottom: none;
}

#navigation a.navigation i { line-height: 41px; }

#navigation a.navigation:hover {
	background-color: rgba(26,188,156,0.7);
	border-bottom: none;
}



/* === WORDSEARCH === */

#wordsearch {
	width: 45%;
	float: left;
}

#wordsearch ul {
	margin: 0px;
	padding: 0px;
}

#wordsearch ul li {
	float: left;
	width: 12%;
	background-color: rgba(0,0,0,.2);
	list-style: none;
	margin-right: 0.5%;
	margin-bottom: 0.5%;
    padding: 0;
    display: block;
    text-align: center;
    color: rgba(255,255,255,0.7);
    text-transform: uppercase;
    overflow: hidden;
    font-size: 24px;
    font-size: 1.6vw;
    font-weight: 300;
    transition: background-color 0.75s ease;
    -moz-transition: background-color 0.75s ease;
    -webkit-transition: background-color 0.75s ease;
    -o-transition: background-color 0.75s ease;
}

#wordsearch ul li.selected {
	background-color: rgba(26,188,156,0.7);
	color: rgba(255,255,255,1);
	font-weight: 400;
}



/* === SEARCH FORM === */

#search { margin-top: 30px; }

#search input[type='text'] {
	width: 88%;
	height: 41px;
	padding-left: 15px;
	padding-rigt: 15px;
	box-sizing: border-box;
	-moz-box-sizing: border-box;
	background-color: rgba(0,0,0,0.2);
	border: none;
	outline: none;
	-webkit-appearance: none;
	font-size: 16px;
	font-weight: 300;
	color: white;
	font-family: 'Source Sans Pro', sans-serif;
	transition: all 0.5s ease;
	-moz-transition: all 0.5s ease;
	-o-transition: all 0.5s ease;
	-webkit-transition: all 0.5s ease;
	border-radius: 0px;
}

#search .input-search {
	width: 10%;
	float: right;
	height: 41px;
	background-color: rgba(0,0,0,0.2);
	outline: none;
	border: none;
	-webkit-appearance: none;
	font-family: 'Source Sans Pro', sans-serif;
	color: white;
	font-weight: 300;
	font-size: 16px;
	cursor: pointer;
	transition: all 0.5s ease;
	-moz-transition: all 0.5s ease;
	-o-transition: all 0.5s ease;
	-webkit-transition: all 0.5s ease;
	text-align: center;
}

#search .input-search:hover {
	background-color: rgba(26,188,156,0.7);
}



/* === RESPONSIVE CSS === */

@media all and (max-width: 899px) {
	#wrap { width: 90%; }
}

@media all and (max-width: 799px) {
	#wrap { width: 90%; height: auto; margin-top: 40px; top: 0%; }
	#wordsearch { width: 90%; float: none; margin:0 auto; }
	#wordsearch ul li { font-size: 4vw; }
	#main-content { float: none; width: 90%; max-width: 90%; margin:0 auto; margin-top: 30px; text-align: justify; }
	#main-content h1 { text-align: left; }
	#search input[type='text'] { width: 84%; }
	#search .input-search { width: 15%; }
}

@media all and (max-width: 499px) {
	#main-content h1 { font-size: 28px; }
}
Javascript
$(function () {
  var liWidth = $("li").css("width");
  $("li").css("height", liWidth);
  $("li").css("lineHeight", liWidth);
  var totalHeight = $("#wordsearch").css("width");
  $("#wordsearch").css("height", totalHeight);
});
causeRepaintsOn = $("h1, h2, h3, p");
$(window).resize(function () {
  causeRepaintsOn.css("z-index", 1);
});
$(window).on('resize', function () {
  var liWidth = $(".one").css("width");
  $("li").css("height", liWidth);
  $("li").css("lineHeight", liWidth);
  var totalHeight = $("#wordsearch").css("width");
  $("#wordsearch").css("height", totalHeight);
});



$(function () {
  /* 4 */
  $(this).delay(1500).queue(function () {
    $(".one").addClass("selected");
    $(this).dequeue();
  })
  /* 0 */.
  delay(500).queue(function () {
    $(".two").addClass("selected");
    $(this).dequeue();
  })
  /* 4 */.
  delay(500).queue(function () {
    $(".three").addClass("selected");
    $(this).dequeue();
  })
  /* P */.
  delay(500).queue(function () {
    $(".four").addClass("selected");
    $(this).dequeue();
  })
  /* A */.
  delay(500).queue(function () {
    $(".five").addClass("selected");
    $(this).dequeue();
  })
  /* G */.
  delay(500).queue(function () {
    $(".six").addClass("selected");
    $(this).dequeue();
  })
  /* E */.
  delay(500).queue(function () {
    $(".seven").addClass("selected");
    $(this).dequeue();
  })
  /* N */.
  delay(500).queue(function () {
    $(".eight").addClass("selected");
    $(this).dequeue();
  })
  /* O */.
  delay(500).queue(function () {
    $(".nine").addClass("selected");
    $(this).dequeue();
  })
  /* T */.
  delay(500).queue(function () {
    $(".ten").addClass("selected");
    $(this).dequeue();
  })
  /* F */.
  delay(500).queue(function () {
    $(".eleven").addClass("selected");
    $(this).dequeue();
  })
  /* O */.
  delay(500).queue(function () {
    $(".twelve").addClass("selected");
    $(this).dequeue();
  })
  /* U */.
  delay(500).queue(function () {
    $(".thirteen").addClass("selected");
    $(this).dequeue();
  })
  /* N */.
  delay(500).queue(function () {
    $(".fourteen").addClass("selected");
    $(this).dequeue();
  })
  /* D */.
  delay(500).queue(function () {
    $(".fifteen").addClass("selected");
    $(this).dequeue();
  });
});