How can I remove the border around the widgets?

One thing to do while you post in a forum would be to name your theme. Of course we can find it from the code (most of the time). But it would make things a lot better.

Goto wordpress theme editor Appearence>>Editor

On the right side where the fines are listed there would be a style.css at the end.

Click on it to edit it.

find this part

.column-center {
height:100%;
overflow:hidden;
padding:0 67px 0 44px;
}

See the

padding : 0 67px 0 44px;

change the 67px to whatever you like. Now note the difference (YY) XXpx = 67px – YYpx

Now find this in the same file

.column-right {
float:right;
width:204px;
}

Now add this

padding-right: YYpx;

YY being the previous difference

Now it should look like

.column-right {
float:right;
padding-right:30px;
width:204px;
}