undefined index

hi to all I try to get data listed out of my database with the statement ... while ($row = mysql_fetch_array($sql)) { $image = $row["imageurl"]; $id = $row["productID"]; $name = $row["cdescription"]; ... If i havent got anything in that field in my database I get the error message in my browser Undefined index: imageurl in ... How can I overcome that problem? Is there a way to define a index if that occurs and make it to not produce that error message? Hope I have explained it understandable enough. If you need to know more details let me know, I would appreciate any help I could get. Thanx P.