Correcting Overfull hbox Errors

Here's a corrected version. Just add spaces between the "word" that was too long
     \documentstyle[12pt]{article}
     \begin{document}
     ``When {\em I} use a word,'' Humpty
---> Dumpty said in rather a scornful tone, 
     ``it means just what I choose it to mean --
     neither more nor less.''
     \end{document}