W3Schools Tryit Editor

<!doctype html>
<html>

<body>
<h1>The flex-basis Property</h1>
<p>Set the initial length of the flex items to 50 pixels, with an exception; set the initial length of the second flex item to 100 pixels:</p>
<div id="main">
 <div>50px</div>
 <div>100px</div>
 <div>50px</div>
 <div>50px</div>
 <div>50px</div>
</div>
</div><div class="naked_ctrl">
<form action="/index.cgi/contrast" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://www.w3schools.com/cssref/tryit.php?filename=trycss3_flex-basis">(->オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://www.w3schools.com/cssref/tryit.php?filename=trycss3_flex-basis" size="22" /></label> <label>モード: <select name="naked_post_mode">
<option value="default">デフォルト</option>
<option value="speech">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast" selected="selected">配色反転</option>
<option value="larger-text">文字拡大</option>
<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
</p>
</form>
</div>		
</body>
</html>