How to remove the white space that is now above the main images on each page?

Question

http://www.nydogworks.net
Hello,
I took over updating some things on my site from my web designer. The main images on each page used to be flush with the navigation bar on each page. Now there is a white space in between each one. Can you tell me how to remove the white space?
<div id="container">
<div id="imgholder"><img src="images/feature-aboutus.jpg" width="951" height="341" alt="" />
</div>
<div id="pageContentNoside">
   <div id="sideSub">
     <form action="form.php" method="post" name="form2" id="form2"> <table width="250" border="0" cellpadding="2" cellspacing="2">
       <tr>
         <td width="273"><h2>Quick Contact</h2></td>
         </tr>
       <tr>
         <td class="mainContent">Your Name</td>
         </tr>
       <tr>
         <td><span class="style9">
           <input name="forname" type="text" class="colorfieldssmall" id="forname" size="20" />
           </span></td>
         </tr>
       <tr>
         <td class="mainContent">Your Email Address* (required)</td>
         </tr>
       <tr>
         <td><span class="style7 style9">
           <input name="admail" type="text" class="colorfieldssmall" id="admail" size="25" />
           </span></td>
         </tr>
       <tr>
         <td class="mainContent">Phone Number</td>
         </tr>
       <tr>
         <td><span class="style7 style9">
           <input name="phone" type="text" class="colorfieldssmall" id="phone" />
           </span></td>
         </tr>
       <tr>
         <td><span class="mainContent">Type of Dog Training</span></td>
         </tr>
       <tr>
         <td class="mainContent"><span class="style9">
           <select name="need" class="colorfieldssmall" id="need">
             <option value="select one">select one</option>
             <option value="Basic Obedience">Basic Obedience</option>
             <option value="Behavior Therapy">Behavior Therapy</option>
             <option value="Board and Train">Board and Train</option>
             <option value="Off Leash Training">Off Leash Training</option>
             <option value="Puppy Training">Puppy Training</option>
             </select>
           </span></td>
         </tr>
       <tr>
         <td> </td>
         </tr>
       <tr>
         <td><div align="left">
           <input type="submit" name="submit" id="submit"  value="Submit" />
           </div>
           </td>
         </tr>
       </table></form>
     <h2><br />
       Dog Training Services<br />
       </h2>
     <ul id="subnav">
       <li><a href="basic-obedience.html">Basic Obedience</a></li>
       <li><a href="dog-behavior-therapy.html">Behavior Therapy</a></li>
       <li><a href="board-and-train-dog-program.html">Board & Train Program</a></li>
       <li><a href="off-leash-training.html">Off Leash Training</a></li>
       <li><a href="puppy-training-program.html">Puppy Training</a></li>
       </ul>
     <br />
     <br />
     <br />
     </div>
  <div id="suggestPost"><a href="https://www.facebook.com/pages/NYDogWorks/219268038151244?fref=ts" ></a></div>
   <div id="mainContent">
     <h1 class="copyrightType">About NY DogWorks</h1><br />
     <h2> <span class="testimonal">The Owner of NYDogWorks</span>      </h2>
     <p><span class="copyrightType"><img src="images/dogpic.jpg" alt="Dog Behavior Therapy" width="183" height="275" class="h_img_float_right" /></span><strong>NYDogWorks L.L.C. is owned and operated by Master Certified Dog Trainer and Behavior Specialist Brian DeMartino. </strong><br />
       <br />
       His training is hands down the best out there. He has become one of the most sought after dog trainers throughout Long Island, Manhattan, &amp; New York.<br />
       <br />
       With over 15 years experience training and rehabilitating some of the toughest cases of dog behaviors. He’s Mastered the Art of teaching top knotch obedience and manners with outstanding results and has developed the most full proof and guaranteed system to fully housebreak any puppy or dog in the shortest amount of time.<br />
       <br />
       He is Certified in dog training and dog behavior and is an Official Evaluator for the American Kennel Club’s (C.G.C) Program.<br />
       <br />
       <br />
       <strong>All About NYDogWorks</strong><br />
       </p>
  <p><br />
  </p>
     <p>NYDogWorks Dog Education, is a Professional Dog Training Company offering dog training for puppies and older dogs through customized in-home training programs by Master Certified Trainers in Nassau County, Suffolk County, Hamptons, Long Island, Manhattan, Brooklyn, Bronx, Queens, Rockland County, Westchester County, Orange County, and Bergen County New Jersey. NYDogWorks offers obedience training, Housebreaking, Manners, socialization for your dog,  Puppy Training and Education, Behavior Therapy, Trick Training, Agility, Complete Off Leash Training, Sport Work, and Personal Protection Training. <br />
       <br />
       <strong><br />
         NYDogWorks Boarding &amp; Training Programs</strong><br />
       </p>
  <p><br />
    We offer boarding and training programs done in the home of owner, Brian DeMartino. This is a customized 2-6 week program to suit your dog's needs, great for someone who feels they do not have the time or patience to train or rehabilitate their dog at their home. This is a 100% guaranteed program. Your dog will stay with us for no additional charge if we feel that he or she has not learned all that was agreed upon. We guarantee that if there is any regression within 3 months of your dog being back home with you, he/she will come back to us for no additional charge.<br />
    <br />
    <a href="board-and-train-dog-program.html">View Boarding &amp; Training Programs</a></p>
     <p><br />
       </p>
     <p><br />
       <br />
  </div>
   <div id="breadCrumbs">
     <p><a href="index.html">Home</a> &gt;  NY DogWorks - About Certified Dog Trainer Brian DeMartino<br />
       <strong>Serving all of Long Island, Nassau &amp; Suffolk County, Manhattan, Brooklyn &amp; Queens</strong></p>
     </div>
</div>
    <div id="footer">
      <div id="footermenu">
      <div id="footermenu1">
      </div>
    </div>
   <div class="phoneNumber" id="copyright"> Copyright © 2014  NY DogWorks</div>
     <div class="websiteDesign" id="sitedesigner">Long Island Website Design by <a href="http://www.wetribet.com" title="Wet Ribet" target="_blank" class="medlink">Wet Ribet</a>     </div>
</div>
</div>

Answer 1

You should be able to add the following snippets of css to your stylesheet to fix that.
In the mainstyle.css file, change...
#imgholder {
width: 950px;
margin-top: 0px;
padding: 0px;
margin-right: auto;
margin-left: auto;
to
#imgholder {
width: 950px;
margin-top: 0px;
padding: 0px;
margin-right: auto;
margin-left: auto;
overflow:hidden;