Example:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Query string from action attribute is killed for GET request</title>
</head>
<body>
<form name="getSearchForm" action="?missed=one" method="get">
<input type="text" name="q" value="s" />
<button class="searchButton" type="submit">GET</button>
</form>
<form name="postSearchForm" action="?missed=one" method="post">
<input type="text" name="q" value="s" />
<button class="searchButton" type="submit">POST</button>
</form>
</body>
</html>
The parameter "missed=one" is missing from URL after clicking a button on a form with GET send method. It is present for POST form though.