Problème pour relié mon code css et html

#container {
    width:780px;
    margin:0 auto;
    position: relative;
}

#content {
    width:520px;
    min-height:500px;
}
a:link, a:visited {
    color:#27b;
    text-decoration:none;
}
a:hover {
    text-decoration:underline;
}
a img {
    border-width:0;
}
#topnav {
    padding:10px 0px 12px;
    font-size:11px;
    line-height:23px;
    text-align:right;
}
#topnav a.signin {
    background:#88bbd4;
    padding:4px 6px 6px;
    text-decoration:none;
    font-weight:bold;
    color:#fff;
    -webkit-border-radius:4px;
    -moz-border-radius:4px;
    border-radius:4px;


*background:transparent url("images/signin-nav-bg-ie.png") no-repeat 0 0;

*padding:4px 12px 6px;
}
#topnav a.signin:hover {
    background:#59B;


*background:transparent url("images/signin-nav-bg-hover-ie.png") no-repeat 0 0;

*padding:4px 12px 6px;
}
#topnav a.signin, #topnav a.signin:hover {


*background-position:0 3px!important;
}

a.signin {
    position:relative;
    margin-left:3px;
}
a.signin span {
    background-image:url("images/toggle_down_light.png");
    background-repeat:no-repeat;
    background-position:100% 50%;
    padding:4px 16px 6px 0;
}
#topnav a.menu-open {
    background:#ddeef6!important;
    color:#666!important;
    outline:none;
}
#small_signup {
    display:inline;
    float:none;
    line-height:23px;
    margin:25px 0 0;
    width:170px;
}
a.signin.menu-open span {
    background-image:url("images/toggle_up_dark.png");
    color:#789;
}

<divid="container">
  <divid="topnav"class="topnav"> Have an account? <ahref="login"class="signin"><span>Sign in</span></a> </div>
  <fieldsetid="signin_menu">
    <formmethod="post"id="signin"action="[https://twitter.com/sessions]">
      <labelfor="username">Username or email</label>
      <inputid="username"name="username"value=""title="username"tabindex="4"type="text">
      </p>
      <p>
        <labelfor="password">Password</label>
        <inputid="password"name="password"value=""title="password"tabindex="5"type="password">
      </p>
      <pclass="remember">
        <inputid="signin_submit"value="Sign in"tabindex="6"type="submit">
        <inputid="remember"name="remember_me"value="1"tabindex="7"type="checkbox">
        <labelfor="remember">Remember me</label>
      </p>
      <pclass="forgot"> <ahref="#"id="resend_password_link">Forgot your password?</a> </p>
      <pclass="forgot-username"> <Aid=forgot_username_link 
title="If you remember your password, try logging in with your email"
href="#">Forgot your username?</A> </p>
    </form>
  </fieldset>
</div>