You can do everything using flash it even makes the html site for you. All you might need to do later is go in the html document and then put in the name of the site for the title bar and some other properties.
If I were you, and I'm not...I would learn how to construct my own html file since the one that is exported when publishing the flash movie is not constructed very well...as far as ilyal goes he is right...you will want to go in later and modify the html and you might even want your movie to popup later on it will all become clear...have an html start page...then have a hyperlink to the movie and have it popup...
you can always create the complete site within Flash 5 .You don't need anything else for the designing or programming part of it, even. Now with Generator , now database connectivity is added even. As for the editing HTML , I don't personnaly see why we should even need to use something else. The only problem one might face is having the movie in full window .. which can be done thru the FS command and just changing the TOPMARGIN="=0" and LEFTMARGIN="0" .
Even forms can be done in Flash 5 as well.