W.P. Ginfo on "Words on the edges"

Hi

article.post, article.page, article.attachment {
    margin-bottom: 15px;
    border-bottom: 1px solid rgb(238, 238, 238);
    margin: 0 30px; /* you may change these values */
}

NOTE!!
ALWAYS Make a backup of your site, before making any changes!!

1. Use FTP to backup the files.
2. Make sure to also backup your database.

http://codex.wordpress.org/Backing_Up_Your_Database

Use a childtheme to make the changes in
Suggestion: use the 'one click childtheme plugin'.