Hello. I have form that contains an input field (Screen) whose name contains an upper-case letter.

Code HTML4Strict:
<html>
<head></head>
 
<body>
 
	<form action="http://localhost/example.php" method="get" name="form" id="form">
		<input value="medium" name="Screen" id="screen"/>
		<button name="upload" type="submit">Upload</button>
	</form>
 
</body>
</html>
So when sent the query is composed as:

http://localhost/example.php?Screen=medium&upload=

Although it works without problem, I want to ask that an upper-case in query string is valid or not?

Thanks.