<form id="form1" name="form1" method="post">
  <p>
    <label for="1">First Name:</label>
    <input type="text" name="first" id="first" />
    <label for="2">Last Name:</label>
    <input type="text" name="last" id="last" />
  </p>
  <p><input type="submit" name="3" id="3" onclick="window.open('http://mywebpage.com/first=val1&.&last=val2')"/>
  </p>
</form>

<form id="form1" name="form1" method="GET" action="http://mywebpage.com/" >