Split out from issue2550648 (Should be possible to search for matching  
several keywords (keyword1 AND keyword2) especially from msg4204 and 
msg4302:

| One thing I noticed is that the (expr) link on the search page 
vanishes once an expression has been entered.

| 1) After (re-)discovering what was already reported in msg4204 (the
disappearance of the "(edit)" link once the keyword value was set), I
attempted to validate the generated HTML, and noticed that it was
invalid. This may be the cause for the reported behavior.