Simple and clean CSS styles for basic HTML layouts

app.css

body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
}
main {
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
}
article {
    margin: 0 auto;
    padding: 20px;
    border: 1px solid #ddd;
    border-radius: 5px;
    background-color: #f9f9f9;
}
h1 {
    font-size: 2em;
    margin-bottom: 0.5em;
}
h2 {
    font-size: 1.5em;
    margin-bottom: 0.5em;
}
h3 {
    font-size: 1.17em;
    margin-bottom: 0.5em;
}
h4 {
    font-size: 1em;
    margin-bottom: 0.5em;
}
h5 {
    font-size: 0.83em;
    margin-bottom: 0.5em;
}
h6 {
    font-size: 0.67em;
    margin-bottom: 0.5em;
}
p {
    margin-bottom: 1em;
}
a {
    color: #007bff;
    text-decoration: none;
}
a:hover {
    text-decoration: underline;
}
blockquote {
    margin: 0;
    padding: 0 1em;
    border-left: 4px solid #ddd;
}
pre {
    margin: 0;
    padding: 1em;
    background-color: #f5f5f5;
    border: 1px solid #ccc;
    border-radius: 5px;
    overflow-x: auto;
}
code {
    font-family: monospace;
    background-color: #f5f5f5;
    padding: 0.2em 0.4em;
    border-radius: 3px;
}
pre code {
    padding: 0;
}
table {
    width: 100%;
    border-collapse: collapse;
}
th, td {
    padding: 0.5em;
    border: 1px solid #ddd;
}
th {
    background-color: #f5f5f5;
}