* {box-sizing: border-box;}

body { 
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
}

.header {
  overflow: hidden;
  background-color: #f1f1f1;
  padding: 20px 10px;
}

.header a {
  float: left;
  color: black;
  text-align: center;
  padding: 12px;
  text-decoration: none;
  font-size: 18px; 
  line-height: 25px;
  border-radius: 4px;
}

.header a.logo {
  font-size: 40px;
  font-weight: bold;
}

.header a:hover {
  background-color: #ddd;
  color: black;
}

.header a.active {
  background-color: dodgerblue;
  color: white;
}

.header-right {
  float: right;
}

@media screen and (max-width: 500px) {
  .header a {
    float: none;
    display: block;
    text-align: left;
  }
  
  .header-right {
    float: none;
  }
}

<!-- Top header code -->

* {
    box-sizing: border-box;
}

body {
  margin: 0;
}

/* Style the header */
.header {
    background-color: #f1f1f1;
    padding: 30px;
    text-align: center;
}

/* Style the top navigation bar */
.topnav {
    overflow: hidden;
    background-color: #333;
	text-align: center;
}

/* Style the topnav links */
.topnav a {
    float: left;
    display: block;
    color: #f2f2f2;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
	
}

/* Change color on hover */
.topnav a:hover {
    background-color: #ddd;
    color: black;
	
}

/* Create three unequal columns that floats next to each other */
.column {
    float: left;
    padding: 20px;
	
}

/* Left and right column */
.column.side {
    width: 15%;
}

/* Middle column */
.column.middle {
    width: 70%;
}

/* Clear floats after the columns */
.row:after {
    content: "";
    display: table;
    clear: both;
}

/* Responsive layout - makes the three columns stack on top of each other instead of next to each other */
@media (max-width: 600px) {
    .column.side, .column.middle {
        width: 100%;
    }
}

/* Style the footer */
.footer1 {
    background-color: #f1f1f1;
    padding: 10px;
    text-align: center;
}

<!--table css code -->

#customers {
  font-family: Arial, Helvetica, sans-serif;
  font-size:16px;
  border-collapse:separate;
  width: 100%;
}

#customers td, #customers th {
  border: 1px solid #ddd;
  padding-top: 2px;
  padding-bottom: 2px;
  padding: 2px;
}

#customers tr:nth-child(even){background-color: #f2f2f2;}

#customers tr:hover {background-color: #ddd;}

#customers th {
  padding-top: 2px;
  padding-bottom: 2px;
  text-align: left;
  background-color:#FF0000;
  color: white;
}


<!-- new table code -->

* {
  box-sizing: border-box;
}

.row {
  margin-left:-5px;
  margin-right:-5px;
}
  
.column {
  float: left;
  width: 50%;
  padding: 5px;
}

/* Clearfix (clear floats) */
.row::after {
  content: "";
  clear: both;
  display: table;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
  width: 100%;
  border: 1px solid #ddd;
}

th, td {
  text-align: left;
  padding: 16px;
}

tr:nth-child(even) {
  background-color: #f2f2f2;
}