How do I remove the blue line?

It seems to be a style in your wrapper id

#wrapper {
-moz-background-clip:border;
-moz-background-inline-policy:continuous;
-moz-background-origin:padding;
background:#333333 url(images/content-bg.png) repeat-y scroll right top;
margin:0 auto !important;
width:960px;
}

The background image content-bg.png has that blue line

Where can I find this in the editor? Sorry I am rather new to this.

it should be in your style.css file which is in:
your-wordpress-folder\wp-content\themes\your-theme-name\style.css

So just change this bit:
background:#333333 url(images/content-bg.png) repeat-y scroll right top;
to:
background:#333333;

Where can I find this in the editor? Sorry I am rather new to this.

edit your style.css using your theme editor in admin panel

url-blog/wp-admin/theme-editor.php

Or if you prefer to access it through your dashboard you navigate to the “Appearance” tab and click on Editor, then select “Stylesheet (style.css)” under styles on the right from the list of theme files

That changed the background color but not the blue line. :/

THANK YOU!!!!! It worked.