
Having a round borders somehow add style to your blog and when used properly it can take your blog design to the next level. Round borders are most likely applied to links to give more impression that it is a button.
-moz-border-radius:10px; *For Mozilla Firefox
-webkit-border-radius: 10px; *For Safari and Google Chrome
You can change radius pixels depending on your need just make sure that you change both -moz and -webkit
Also make sure that this two have the same value. Example code:
#header-wrapper {
width:600px;
margin:0 auto;
border: 1px solid #000000;
-moz-border-radius: 7px;
-webkit-border-radius: 7px;
background: #ffffff;
}