This obviously does not work if the blank lines contain tabs or blanks. Many web pages (e.g. http://www.guardian.co.uk/) contain these white lines, as a result of a faulty HTML editor.
Remove white space using regular expression as follows:
change pattern: [\t ]+$ into nothing.
where [\t ] matches either tab or space. '+' matches one or more occurrences, and '$' marks the end of line.
Then use notepad++/textFX to remove single or extra empty lines. Be sure that these blank lines are not significant in the given context.