When assisting people on the Joomla Forums, it's helpful if they can provide a link to their site so I can see the issue myself.  In a lot of cases, this isn't possible because they are developing locally or the server is not accessible to the outside world.  The next best thing is to get a screenshot of the issue.

There are a lot of resources out on the web that describe how to take a screenshot on many different operating systems:

Wikipedia Screenshot

Windows XP Screenshot

Mac OS X Screenshot

Once you have your screenshot, it may be too large to post on the forums.  There are also many tools out on the web (or already on your computer) to help resize, crop, and convert images:

Windows - How to Convert BMP to JPG Using Microsoft Paint

Mac OS X - Converting to TIFF, JPG, or Photoshop

Once you have your screenshot, you can upload it to your post and hopefully get an answer!