In this form we have two parts. There is a section on the left and the forms are inside it. The other part is on the right and has a pink background. You can write down any text you need or the rules required to register and log in to your website in this section.


HTML
<!-- This script got from www.devanswer.com -->
<div class="container" id="container">
    <div class="form-container sign-up-container">
        <form action="#">
            <h1>Create Account</h1>
            <div class="social-container">
                <a href="#" class="social"><i class="fa fa-facebook-f"></i></a>
                <a href="#" class="social"><i class="fa fa-instagram"></i></a>
                <a href="#" class="social"><i class="fa fa-linkedin-in"></i></a>
            </div>
            <span>or use your email for registration</span>
            <input type="text" placeholder="Name" />
            <input type="email" placeholder="Email" />
            <input type="password" placeholder="Password" />
            <button>Sign Up</button>
        </form>
    </div>
    <div class="form-container sign-in-container">
        <form action="#">
            <h1>Sign in</h1>
            <div class="social-container">
                <a href="#" class="social"><i class="fab fa-facebook-f"></i></a>
                <a href="#" class="social"><i class="fab fa-instagram"></i></a>
                <a href="#" class="social"><i class="fab fa-linkedin-in"></i></a>
            </div>
            <span>or use your account</span>
            <input type="email" placeholder="Email" />
            <input type="password" placeholder="Password" />
            <a href="#">Forgot your password?</a>
            <button>Sign In</button>
        </form>
    </div>
    <div class="overlay-container">
        <div class="overlay">
            <div class="overlay-panel overlay-left">
                <h1>Welcome Back!</h1>
                <p>To keep connected with us please login with your personal info</p>
                <button class="ghost" id="signIn">Sign In</button>
            </div>
            <div class="overlay-panel overlay-right">
                <h1>Hello, Friend!</h1>
                <p>Enter your personal details and start journey with us</p>
            </div>
        </div>
    </div>
</div><div id="bcl"><a style="font-size:8pt;text-decoration:none;" href="http://www.devanswer.com">Developers Answer</a></div>
                        

CSS
* {
	box-sizing: border-box;
}
body {
	background: #f6f5f7;
	display: flex;
	justify-content: center;
	align-items: center;
	flex-direction: column;
	font-family: 'Montserrat', sans-serif;
	height: 100vh;
	margin: -20px 0 50px;
}
h1 {
	font-weight: bold;
	margin: 0;
}
h2 {
	text-align: center;
}
p {
	font-size: 14px;
	font-weight: 100;
	line-height: 20px;
	letter-spacing: 0.5px;
	margin: 20px 0 30px;
}
span {
	font-size: 12px;
}
a {
	color: #333;
	font-size: 14px;
	text-decoration: none;
	margin: 15px 0;
}
button {
	border-radius: 20px;
	border: 1px solid #FF4B2B;
	background-color: #FF4B2B;
	color: #FFFFFF;
	font-size: 12px;
	font-weight: bold;
	padding: 12px 45px;
	letter-spacing: 1px;
	text-transform: uppercase;
	transition: transform 80ms ease-in;
}
button:active {
	transform: scale(0.95);
}
button:focus {
	outline: none;
}
button.ghost {
	background-color: transparent;
	border-color: #FFFFFF;
}
form {
	background-color: #FFFFFF;
	display: flex;
	align-items: center;
	justify-content: center;
	flex-direction: column;
	padding: 0 50px;
	height: 100%;
	text-align: center;
}
input {
	background-color: #eee;
	border: none;
	padding: 12px 15px;
	margin: 8px 0;
	width: 100%;
}
.container {
	background-color: #fff;
	border-radius: 10px;
	box-shadow: 0 14px 28px rgba(0, 0, 0, 0.25), 0 10px 10px rgba(0, 0, 0, 0.22);
	position: relative;
	overflow: hidden;
	width: 768px;
	max-width: 100%;
	min-height: 480px;
}
.form-container {
	position: absolute;
	top: 0;
	height: 100%;
	transition: all 0.6s ease-in-out;
}
.sign-in-container {
	left: 0;
	width: 50%;
	z-index: 2;
}
.container.right-panel-active .sign-in-container {
	transform: translateX(100%);
}
.sign-up-container {
	left: 0;
	width: 50%;
	opacity: 0;
	z-index: 1;
}
.container.right-panel-active .sign-up-container {
	transform: translateX(100%);
	opacity: 1;
	z-index: 5;
	animation: show 0.6s;
}
@keyframes show {
	0%, 49.99% {
		opacity: 0;
		z-index: 1;
	}
	50%, 100% {
		opacity: 1;
		z-index: 5;
	}
}
.overlay-container {
	position: absolute;
	top: 0;
	left: 50%;
	width: 50%;
	height: 100%;
	overflow: hidden;
	transition: transform 0.6s ease-in-out;
	z-index: 100;
}
.container.right-panel-active .overlay-container {
	transform: translateX(-100%);
}
.overlay {
	background: #FF416C;
	background: -webkit-linear-gradient(to right, #FF4B2B, #FF416C);
	background: linear-gradient(to right, #FF4B2B, #FF416C);
	background-repeat: no-repeat;
	background-size: cover;
	background-position: 0 0;
	color: #FFFFFF;
	position: relative;
	left: -100%;
	height: 100%;
	width: 200%;
	transform: translateX(0);
	transition: transform 0.6s ease-in-out;
}
.container.right-panel-active .overlay {
	transform: translateX(50%);
}
.overlay-panel {
	position: absolute;
	display: flex;
	align-items: center;
	justify-content: center;
	flex-direction: column;
	padding: 0 40px;
	text-align: center;
	top: 0;
	height: 100%;
	width: 50%;
	transform: translateX(0);
	transition: transform 0.6s ease-in-out;
}
.overlay-left {
	transform: translateX(-20%);
}
.container.right-panel-active .overlay-left {
	transform: translateX(0);
}
.overlay-right {
	right: 0;
	transform: translateX(0);
}
.container.right-panel-active .overlay-right {
	transform: translateX(20%);
}
.social-container {
	margin: 20px 0;
}
.social-container a {
	border: 1px solid #DDDDDD;
	border-radius: 50%;
	display: inline-flex;
	justify-content: center;
	align-items: center;
	margin: 0 5px;
	height: 40px;
	width: 40px;
}
footer {
	background-color: #222;
	color: #fff;
	font-size: 14px;
	bottom: 0;
	position: fixed;
	left: 0;
	right: 0;
	text-align: center;
	z-index: 999;
}
footer p {
	margin: 10px 0;
}
footer i {
	color: red;
}
footer a {
	color: #3c97bf;
	text-decoration: none;
}