[Logikos]

If its powered by vB then

                <!-- login form -->
                <form action="login.php" method="post" onsubmit="md5hash(vb_login_password,vb_login_md5password,vb_login_md5password_utf)">
                <script type="text/javascript" src="clientscript/vbulletin_md5.js"></script>
                <table cellpadding="0" cellspacing="$stylevar[formspacer]" border="0">
                <tr>
                        <td class="smallfont">$vbphrase[username]</td>
                        <td><input type="text" class="button" name="vb_login_username" id="navbar_username" size="14" accesskey="u" tabindex="1" value="$vbphrase[username]" onfocus="if (this.value == '$vbphrase[username]') this.value = '';" /></td>
                </tr>
                <tr>
                        <td class="smallfont">$vbphrase[password]</td>
                        <td><input type="password" class="button" name="vb_login_password" size="14" accesskey="p" tabindex="2" /><br><input type="submit" class="button" value="$vbphrase[log_in]" tabindex="4" title="$vbphrase[enter_username_to_login_or_register]" accesskey="s" /></td>
                </tr>
                </table>
                <input type="hidden" name="s" value="$session[sessionhash]" />
                <input type="hidden" name="do" value="login" />
                <input type="hidden" name="forceredirect" value="1" />
                <input type="hidden" name="vb_login_md5password" />
                <input type="hidden" name="vb_login_md5password_utf" />
                </form>
                <!-- / login form -->

Should work fine, or at least it would be in the navbar template, which is globaly called on all main templates.