You have to number your tabindex
in the order you'd like them to go.
<input type="text" name="name" id="name" value="" tabindex="1">
<input type="text" name="email" id="email" value="" tabindex="2">
<textarea cols="40" rows="8" name="message" id="message" tabindex="3"></textarea>
<input type="text" name="captcha" id="captcha" tabindex="4"/>
<input class="submit-button" type="submit" value="Submit" tabindex="5">
etc.
Right now you have two tabindex
es set to 1, so they will go first, as they are the only ones with a defined tabindex.