https://ajuda.forumeiros.com/t13876-

/* Caixa de login flutuante - Jeffrey Fórum dos Fóruns - INICIO */
#flutuante
{position:absolute; bottom:78%; margin-left:75%; float:left; border-radius:5px;-moz-border-radius:5px;-webkit-border-radius:5px;background-color:#fff;padding:0 0 2px 0;z-index:10;}

#pageshare .sbutton {float:left;clear:both;margin:5px 5px 0 5px;}
.fb_share_count_top {width:100px !important;}
.fb_share_count_top, .fb_share_count_inner {-moz-border-radius:3px;-webkit-border-radius:3px;}
.FBConnectButton_Small, .FBConnectButton_RTL_Small {width:49px !important; -moz-border-radius:3px;-webkit-border-radius:3px;}
.FBConnectButton_Small .FBConnectButton_Text {padding:2px 2px 3px !important;-moz-border-radius:3px;-webkit-border-radius:3px;font-size:8px;}
/* Caixa de login flutuante - Jeffrey Fórum dos Fóruns - FIM */

Código:

<div id="flutuante"><div class='sbutton' id='fb'><div class="module"><div class="inner"><span class="corners-top"><span></span></span><div class="h3" style="text-align:left;">Login</div><span></span></p><p><form action="/login" method="post" name="form_login">

<label for="username"><b>Nome de usuário</b>:</label></dt><dd><input type="text" tabindex="1" name="username" id="username" size="25" maxlength="40" value="" class="inputbox autowidth" /></dd></dl><dl><dt><label for="password"><b>Senha</b>:</label></dt><dd><input type="password" tabindex="2" id="password" name="password" size="25" maxlength="25" class="inputbox autowidth" />

<br></br>

<dd><input type="hidden" name="redirect" value="" /><input type="hidden" name="query" value="" /><input type="submit" name="login" tabindex="6" value="Login" class="button1" /></dd><p>

<a href="/register"><img src ="http://2img.net/i/fa/admin/icones/small_ico/utilisateur.png"/> Registrar-se</a> - <a href="/profile?mode=sendpassword"><img src ="http://2img.net/i/fa/admin/icones/small_ico/configuration.png"/> Esqueci a senha</a></p>

</form>
<span class="corners-bottom"><span></span></span></div></div><div style="height:2px"></div></div></div>