HTML Code:
<a target="_blank" href="http://img838.imageshack.us/i/capturemz.jpg/">
<span title="" onclick="window.location.href='http://img838.imageshack.us/img838/5354/capturemz.th.jpg';return false" class="aimgbox">
<img border="0" class="aimg" alt="" src="http://img838.imageshack.us/img838/5354/capturemz.th.jpg">
</span>
</a>
because of the extraneous span onclick method added, clicking the image opens the image instead of the link.
Steps to reproduce:
Post an img
surround it with url
Click the image
What happens:
browser loads the image
Expected:
browser will load the url (can be an image)
It works properly in here
https://vborg.vbsupport.ru/misc.php?do=bbcode#imgcode
So you have some custom code that is adding the extra span with onclick and hindering this functionality in posts.