Edit in JSFiddle

$("img").on("error", function() {
  $(this).attr({
    alt: this.src,
    src: "http://i.imgur.com/LC55jpd.jpg"
  });
});

<div class="contents" align="center">
  <a href="https://scontent-b-hkg.xx.fbcdn.net/hphotos-xfp1/v/t1.0-9/10428640_1165769456804846_4072931005434772621_n.png?oh=4c96a7eff237016d2ea36f48524f5517&amp;oe=5594D72D" class="fa_fancybox"><img src="https://scontent-b-hkg.xx.fbcdn.net/hphotos-xfp1/v/t1.0-9/10428640_1165769456804846_4072931005434772621_n.png?oh=4c96a7eff237016d2ea36f48524f5517&amp;oe=5594D72D" alt=""></a>
  <br>
  <br>
  <a href="https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10924752_1165769480138177_6172584555470732890_n.png?oh=fb26506834f1a913ecdd5021ceded14a&amp;oe=5549B5D3&amp;__gda__=1431238890_9473873e5f728157e8cec6bd92d21f71" class="fa_fancybox"><img src="https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10924752_1165769480138177_6172584555470732890_n.png?oh=fb26506834f1a913ecdd5021ceded14a&amp;oe=5549B5D3&amp;__gda__=1431238890_9473873e5f728157e8cec6bd92d21f71" alt=""></a>
  <br>
  <br>
  <a href="https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/10959868_1165769473471511_6919101813930502412_n.png?oh=84ba6c99604a7556562fd53ddec24aaf&amp;oe=555F2E7A&amp;__gda__=1432329258_fa56e0d47938f88d730350dcf0598881" class="fa_fancybox"><img src="https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/10959868_1165769473471511_6919101813930502412_n.png?oh=84ba6c99604a7556562fd53ddec24aaf&amp;oe=555F2E7A&amp;__gda__=1432329258_fa56e0d47938f88d730350dcf0598881" alt=""></a>
  <br>
  <br>
  <a href="https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/10985588_1165769466804845_208538922122039102_n.png?oh=ce4f6ea3b6bb57056374178fdcf915d9&amp;oe=556365A8&amp;__gda__=1430953761_0e88aeb92d953f41ecff38e94de86316" class="fa_fancybox"><img src="https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/10985588_1165769466804845_208538922122039102_n.png?oh=ce4f6ea3b6bb57056374178fdcf915d9&amp;oe=556365A8&amp;__gda__=1430953761_0e88aeb92d953f41ecff38e94de86316" alt=""></a>
  <br>
  <br>
  <a href="https://scontent-b-hkg.xx.fbcdn.net/hphotos-xap1/v/t1.0-9/1484662_1165769470138178_7517070416271611433_n.png?oh=880be4d0185e57f53718713c7dcab9c4&amp;oe=555DF524" class="fa_fancybox"><img src="https://scontent-b-hkg.xx.fbcdn.net/hphotos-xap1/v/t1.0-9/1484662_1165769470138178_7517070416271611433_n.png?oh=880be4d0185e57f53718713c7dcab9c4&amp;oe=555DF524" alt=""></a>
  <br>
  <br>
  <a href="https://scontent-a-hkg.xx.fbcdn.net/hphotos-xap1/v/t1.0-9/10690132_1165769463471512_7843301480197566412_n.png?oh=f27f0196a1cee8777cad41ae1e79b682&amp;oe=5564651C" class="fa_fancybox"><img src="https://scontent-a-hkg.xx.fbcdn.net/hphotos-xap1/v/t1.0-9/10690132_1165769463471512_7843301480197566412_n.png?oh=f27f0196a1cee8777cad41ae1e79b682&amp;oe=5564651C" alt=""></a>
  <br>
  <br>
  <a href="https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/10941422_1165769460138179_4375243067430916179_n.png?oh=c88e3af9cb76be3e4a72966f45e40db6&amp;oe=5559229E&amp;__gda__=1432310990_f6e7ce59e40f674afc70678028678608" class="fa_fancybox"><img src="https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/10941422_1165769460138179_4375243067430916179_n.png?oh=c88e3af9cb76be3e4a72966f45e40db6&amp;oe=5559229E&amp;__gda__=1432310990_f6e7ce59e40f674afc70678028678608" alt=""></a>
  <br>
  <br>
</div>