How to style a button

HTML & CSS
20

I tried this but obviously I did not understand it. When I click I end up back on the page I want to close

<style>
#close{

margin:0 auto;
margin-top:100px;
border:solid gray 5px;
background-color:#F1E3D5;
color:black;
max-width:60%;
padding:30px 0 20px 0;
}

#close p{
text-align:center !important;
line-height:160%;

}

#close b{
color:crimson;
font-size:20px;
}
.advert{

padding-top:20px;
}
#close span{
text-align:center;
margin:0 auto;
}
</style>
<div id="close">

<a href="#" onclick="closeWin()"><p> To return to the previous page <br><b>close this tab only</b><br>Press the little x at the top in the tab<br> not in the top right corner.</p>

 </a>

</div>