I noticed recently a comprehensive list of bug present in IE 6 bugs which have been fixed in the latest release of IE7 (http://blogs.msdn.com/ie/archive/2006/08/22/712830.aspx)

A very interesting read, clearly there are lots of differences between the rendering engine of IE6 and IE7.   It seems likely that it will be these issues that will be keeping client side web developers busy in the near future.  As we start to spend more time on ensuring websites render correctly in the most recent version of IE and Firefox the above list of bugs will become increasingly common in websites.

Its well work reading the above list and getting to know the bugs now as they are likely to crop up time and time again in the coming months / years.

The list mentions that the "list-item whitespace bug" has been fixed. (white space in mark up putting blank space randomly in the content of rendered content).  However I noticed the whitespace bug occurring in IE7 in an unordered list menu which incorporated images!  So clearly whitespace bugs do still occur in IE7.  It might be that they this bug occurs in less situations.  However they say it does sometimes occur in both IE6 and 7.....

To ensure that you avoid the whitespace bug in IE6 AND IE7 remove all whitespace from markup where images are encased in links.  For example rewrite this:

<ul>
    <li>
    <a href="#" ><img src="img.gif" alt="Blah" /></a>
    </li>
</ul>

As:

<ul><li><a href="#" ><img src="img.gif" alt="Blah" /></a></li></ul>

(Same markup but with white space removed)