Not that you are going to worry about this too much if the search input is only reused on a page returned to that very user, but you may want to do something to escape any HTML that is included in the user input before it gets sent back to the browser (in an HTML document). At best, it will goof up the display (i.e. the browser will interpret the tags as tags). At worst, if one user is allowed to enter input that will be output to another user there is significant potential for foul play (javascript, pictures of Barney... people do weird stuff if this hole is open).