Question: I have an absolute positioned popup (hover over "ice white" image to see popup) which has css left:50%. Now this should appear in the middle of page but doesn't. Any suggestions please? Thanks in advance.

Answer: 
Lol, no. The *left side* of the image appears at 50% of the page width. Hence; *left: 50%*.

In order to center your image, set *margin: auto* instead.
Your code is working correctly. The popup is being positioned with left of 50% ... of the TD tag it's nested inside. 

Try either taking the popup out of the table, or setting it to 50% of the document width instead. (Your javascript is minified and unreadable to me, or I'd help further.)