Tweak my Github with Stylish

github-tweaks.css

@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document domain("github.com") {
  .container {
    width: 97% !important;
  }
  .pagehead {
    margin-left: 40px !important;
  }
  .gh-header-back {
    margin-left: 0px !important;
  }
  .container > .repository-content, .container > .repo-container > .repository-content {
    width: 90% !important;
  }
  .container > .with-full-navigation > .repository-content, .pull-request-composer .discussion-topic {
    width: 87% !important;
  }
  .column-main, .repo-settings-content, .settings-content, .js-new-issue-form > .discussion-timeline-cols > .main {
    width: 84% !important;
  }
  .new-discussion-timeline .discussion-timeline, .timeline-new-comment {
    width: 100% !important;
    max-width: 100% !important;
  }
  .news {
    width: 78% !important;
  }
  .list-group-item-meta .branch-name .css-truncate-target {
    max-width: 100% !important;
  }
  textarea.comment-form-textarea {
    font-family: Consolas,"Liberation Mono",Menlo,Courier,monospace;
  }
  div.discussion-sidebar {
    width: 0% !important;
    visibility: hidden;
  }
}

@-moz-document domain("gist.github.com") {
  .column {
    width: 91% !important;
  }
  .file-contents {
    width: 98% !important;
  }
  .gist-content {
    width: 87% !important;
  }
}