Using pure HTML and CSS in modal - html

Question

I found this modal http://codepen.io/imprakash/pen/GgNMXO pure html and css no js. It's all great and all but how can I make it trigger without using a button or link? I want it to pop up to welcome visitors once the website load.
<div id="popup1" class="overlay">
<div class="popup">
<h2>Here i am</h2>
<a class="close" href="#">×</a>
<div class="content">
Thank to pop me out of that button, but now i'm done so you can close this window.
</div>
</div>

Answer 1

i modified your codepen
body {
font-family: Arial, sans-serif;
background: url(http://www.shukatsu-note.com/wp-content/uploads/2014/12/computer-564136_1280.jpg) no-repeat;
background-size: cover;
height: 100vh;
}
h1 {
text-align: center;
font-family: Tahoma, Arial, sans-serif;
color: #06D85F;
margin: 80px 0;
}
.box {
width: 40%;
margin: 0 auto;
background: rgba(255,255,255,0.2);
padding: 35px;
border: 2px solid #fff;
border-radius: 20px/50px;
background-clip: padding-box;
text-align: center;
}
.button {
font-size: 1em;
padding: 10px;
color: #fff;
border: 2px solid #06D85F;
border-radius: 20px/50px;
text-decoration: none;
cursor: pointer;
transition: all 0.3s ease-out;
}
.button:hover {
background: #06D85F;
}
.overlay {
position: fixed;
top: 0;
bottom: 0;
left: 0;
right: 0;
background: rgba(0, 0, 0, 0.7);
transition: opacity 500ms;
visibility: hidden;
opacity: 0;
}
.overlay:not(:target) {
visibility: visible;
opacity: 1;
}
.popup {
margin: 70px auto;
padding: 20px;
background: #fff;
border-radius: 5px;
width: 30%;
position: relative;
transition: all 5s ease-in-out;
}
.popup h2 {
margin-top: 0;
color: #333;
font-family: Tahoma, Arial, sans-serif;
}
.popup .close {
position: absolute;
top: 20px;
right: 30px;
transition: all 200ms;
font-size: 30px;
font-weight: bold;
text-decoration: none;
color: #333;
}
.popup .close:hover {
color: #06D85F;
}
.popup .content {
max-height: 30%;
overflow: auto;
}
#media screen and (max-width: 700px){
.box{
width: 70%;
}
.popup{
width: 70%;
}
}
<h1>Popup/Modal Windows without JavaScript</h1>
<div class="box">
<a class="button" href="#popup1">Let me Pop up</a>
</div>
<div id="popup1" class="overlay">
<div class="popup">
<h2>Here i am</h2>
<a class="close" href="#popup1">×</a>
<div class="content">
Thank to pop me out of that button, but now i'm done so you can close this window.
</div>
</div>
</div>

Answer 2

You could make it with animations. A quick example:
#popup1 {
animation-name: welcome;
animation-duration: 2s;
}
#keyframes welcome {
0% {
opacity: 0;
}
30% {
opacity: 0;
}
100% {
opacity: 1;
}
}
<div id="popup1" class="overlay">Hey!</div>

Answer 3

As the technique uses :target psuedo class, you can directly target with appending the id of that pop up element.
Try this, http://codepen.io/imprakash/pen/GgNMXO#popup1
Just appended #popup1 to target. Thus as soon as you open, popup will be targeted and opened.