Adding css to pages with a certain category

HTML & CSS
2

That selector will have no effect on that page.

I see 2 different tags each having only one of each class

<article id="post-2935" class="post-2935 campaign type-campaign status-publish has-post-thumbnail hentry cp-categs-education">
  <div class="cmsms_campaign_cont">
    <figure class="cmsms_img_wrap">
      <a href="http://109.199.118.79/~muslimah/umcwales.com/wp-content/uploads/2015/05/elective-home-education-m.jpg" title="Elective Home Education" class="cmsms_img_link preloader highImg">
        <img width="860" height="400" src="http://109.199.118.79/~muslimah/umcwales.com/wp-content/uploads/2015/05/elective-home-education-m-860x400.jpg" class="full-width wp-post-image" alt="Elective Home Education" title="Elective Home Education" />
      </a>
    </figure>
    <div class="campaign_meta_wrap">

Depending on what you are trying to target you will need to add a comma, space, (or other) or modify the HTML