<STYLE TYPE="text/css">

body {margin-left: 5mm; margin-right: 5mm; margin-top: 5mm;
font-family: Calibri, Arial, Helvetica; font-size=large}
h1 {font-family: Arial, Helvetica; font-size=xx-large}
h2 {font-family: Arial, Helvetica; font-size=xx-large}
h3 {font-family: Arial, Helvetica; font-size=x-large}
p, br, ul, li, td, th, blockquote {font-family: Calibri, Arial, Helvetica}

b {color: brown}
div class ="p"

hrb {width: 90%; height: 10px; background-color:#ff0000}
hrr {border: 0; width: 100%;  color: #ff0000; background-color: #ff0000; height: 5px;}
hrb {border: 0; width: 100%;  color: #0000ff; background-color: #0000ff; height: 5px;}
hrg {border: 0; width: 100%;  color: #00cc00; background-color: #00cc00; height: 5px;}
.hidden{
       display:none;
    }
.sel-none{
user-select: none; /* supported by Chrome and Opera */
-webkit-user-select: none; /* Safari */
-khtml-user-select: none; /* Konqueror HTML */
-moz-user-select: none; /* Firefox */
-ms-user-select: none;
}

br.cb {clear: both;}
<img style="border:5px solid black">

.center {
  margin-left: auto;
  margin-right: auto;
}
</STYLE>