the second example shows you how you how you could use the could to place an image on your page. the code would be placed into whichever .php file it correlates to and the custom key would be placed into a post.

and

<img src=”http://yourdomain.com/wp-content/uploads/ID, $key, true); ?>.jpg”>

where should i put this code?? and wat value i put at the “custom field”..my theme request me to put custom key to make the image preview posible but i have no idea wat is custome key is..

Thanks for the clear explanation. A question that will reveal my ignorance – sorry!–
Isn’t just as easy to simply put the image URL in the post ? Why go to the hassle of setting up a custom key to accomplish this?

Second question: (again -sorry about the level of ignorance): Regarding custom keys and use of wpdb objects to access them – lets say there are several custom keyed list items to list on the sidebar just as an example – should you do repetitive queries to get each, or one big query with several joins and then loop the array of results to get them? Probably not making myself clear. If you do repetitive queries do you have to flush or reset the mySQL database search between each query? And I can’t find any info about the structure of the query $object result ($pageposts for example) – to know how to get at the array.
Finally there seems to be a delay between adding a key/value to a page and the appearance of the desired list item on the site. Why?

Perhaps there’s a tutorial on this other than that which appears on the Codex but I haven’t been able to find such

thanks very much in advance

Bob