<!DOCTYPE html>
<html>
<head>
<style>
.grid-container {
display: grid;
grid-template-columns: 100px 100px 100px;
grid-template-rows: 100px 100px 100px;
}
.grid-item {
border: 1px solid;
}
.item1 {
grid-column-start: 1;
grid-column-end: 4;
border: 1px solid;
}
</style>
</head>
<body>
<div class="grid-container">
<div class="item1">A</div>
<div class="grid-item">B</div>
<div class="grid-item">C</div>
<div class="grid-item">D</div>
<div class="grid-item">E</div>
<div class="grid-item">F</div>
</div>
</body>
</html>