Ignore Whitespace: When checked, Ignore Whitespace allows Search and Replace to ignore extra spaces and \r (CR), \n (LF), \t (Tab) characters between whole words. This allows you to easily find, for example, the string "IMG src=" even if "IMG" and "src=" are on adjacent lines &/or separated by more than one space. Your search string must have one or more of the whitespace characters in the position where the whitespace exists in your file(s) for Ignore Whitespace to work. Note that if you do a replace with Ignore Whitespace on, the intervening extra spaces, & \r \n \t characters are not replaced. Therefore, to maintain these during a replace, use a Regular Expression search/replace. When Regular Expressions is turned on, Ignore Whitespace is not available.