CSS - Cascading Style Sheets

2 min readArticle

CSS controls the visual presentation of HTML documents. Knowing CSS is useful if you're building phishing pages, captive portals, evil twin login pages, or just need to clone a website for a social engineering engagement. Also useful for web app pentesting to understand how front-ends are built.

Core Concepts

Selectors - target which HTML elements to style
Properties - what aspect to change (color, size, position)
Values - what to set it to
Cascade - rules can conflict; specificity and order determine which wins
Box Model - every element is a box: content, padding, border, margin

Basic Syntax

css

/* Select by element type */
h1 {
    color: #333333;
    font-size: 2rem;
    font-family: Arial, sans-serif;
}

/* Select by class */
.login-box {
    width: 400px;
    margin: 0 auto;
    padding: 30px;
    border: 1px solid #ccc;
    border-radius: 8px;
    background: #fff;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

/* Select by ID */
#submit-btn {
    background-color: #0078d4;
    color: white;
    border: none;
    padding: 10px 20px;
    cursor: pointer;
}

/* Hover state */
#submit-btn:hover {
    background-color: #005a9e;
}

Flexbox (Most Useful Layout Method)

css

.container {
    display: flex;
    justify-content: center;  /* horizontal alignment */
    align-items: center;      /* vertical alignment */
    min-height: 100vh;        /* full viewport height */
    flex-direction: column;   /* stack vertically */
    gap: 20px;
}

Cloning a Login Page (Phishing Context)

When cloning a site for social engineering demos, use browser DevTools (F12) to copy CSS. Key things to grab:

Font families and sizes
Color scheme (inspect body, main containers)
Button styles
Input field styling
Logo/image paths

css

/* Make page look like Microsoft login */
body {
    font-family: 'Segoe UI', sans-serif;
    background: #f2f2f2;
    margin: 0;
}

Responsive Design

css

/* Mobile-friendly */
@media (max-width: 768px) {
    .login-box {
        width: 90%;
        padding: 20px;
    }
}

CSS for Captive Portals

Evil twin captive portals need CSS to look convincing. Key patterns:

Center a card on screen using flexbox
Match the target's brand colors
Make input fields look native
Match button styling exactly

Common Properties Quick Ref

Property	Example
`color`	`#ff0000`, `red`, `rgb(255,0,0)`
`background-color`	`#ffffff`
`font-size`	`16px`, `1.2rem`
`padding`	`10px 20px` (top/bottom left/right)
`margin`	`0 auto` (center horizontally)
`display`	`flex`, `block`, `none`
`position`	`fixed`, `absolute`, `relative`