If you are designing a site that you want to
rank well in search engine, chances are a pure flash design
will not be beneficial to you. Although search engines are
getting better all the time, they still have trouble spidering
and gathering information from flash site. This difficulty
usually results in flash page performing below that of normal
text based HTML web sites.
Not everyone has the Macromedia
Flash player installed, so it is a possibility that you will
alienate some of your potential to audience if you go with a pure
flash design. Often web developers will create two sites: flash
and normal HTML to prevent losing any visitors.
Flash can also be very computationally intensive making
animation and videos look great on your top of the line
computer, but visitors with older technology may only see a
choppy, slugglish slideshow that leaves them with a bad feeling.