NOTE: this process is obsolete, from what I can gather it was only supported in MSIE6, and possibly MSIE7.

Use of this tag will disable the Image Toolbar (normally accessed via right-click) within MSIE. Typically it is enabled whenever an image larger than 130×130 is displayed.

Implementation:
Add the following to the <head> section of your webpage(s):
<meta http-equiv="imagetoolbar" content="false" />

Alternately, you COULD use some proprietary MSIE attributes on the <img /> tag.
<img src="..." galleryimg="false" />

Even when you use the META tag to disable this feature for all images, you can explicitly re-enable it with the following proprietary tag…
<img src="..." galleryimg="true" />

References: