For the right site Flash is ideal. If your website has to convey a sophistication of design Flash can be the only solution. If your website is primarily about textual content then a standard html site may work better.
Graphics designers, muliti-media companies and real-estate companies have all used flash to good effect. An artist my be seduced by the idea of a graphics heavy flash site. Often we find that a tastefully designed standard html site that shows off the artist’s work is the most effective solution.
Another side of flash is rich interactive content forms. This is just another way of doing what is commonly referred to as AJAX. You can read a dicussion of this topic in the database section.