ah I can see what you mean, this my alternative solution :
open this file :
modules/mod_poplogin/tmpl/mod_poplogin.css, find this code :
.tppopsigninbutton,
.tppoploginbutton {
background:url(bgtppoploginbutton.png) no-repeat right 50% #00A8C6;
width: 140px;
color: #FFF!important;
text-shadow:0px 1px 0px #276891;
-webkit-border-radius: 5px;
-moz-border-radius: 5px;
border-radius: 5px;
border: none;
padding: 10px 10px!important;
cursor: pointer;
font-size: 16px!important;
float: left;
text-align: left;
}
.tppopsigninbutton {
background:url(bgtppoploginbutton.png) no-repeat right 50% #6CB329;
}
.tppopsigninbutton a,
.tppopsigninbutton a:visited {
color: #FFF!important;
font-size: 16px!important;
}
.tppopsigninbutton:hover,
.tppoploginbutton:hover {
background-color: #000;
color: #FFF!important;
text-shadow:none;
}
change that to :
.tppopsigninbutton a,
.tppoploginbutton {
background:url(bgtppoploginbutton.png) no-repeat right 50% #00A8C6;
width: 140px;
color: #FFF!important;
text-shadow:0px 1px 0px #276891;
-webkit-border-radius: 5px;
-moz-border-radius: 5px;
border-radius: 5px;
border: none;
padding: 10px 10px!important;
cursor: pointer;
font-size: 16px!important;
float: left;
text-align: left;
}
.tppopsigninbutton a{
background:url(bgtppoploginbutton.png) no-repeat right 50% #6CB329;
}
.tppopsigninbutton a,
.tppopsigninbutton a:visited {
color: #FFF!important;
font-size: 16px!important;
}
.tppopsigninbutton a:hover,
.tppoploginbutton:hover {
background-color: #000;
color: #FFF!important;
text-shadow:none;
}