Charity here.
I have a question about a type of flashing images.
Do any of you know how to make lightning flash down from the top of the page in the bg?
Let me know, please.

do you have an example of a page that has that effect?
I'm not sure you want Flash for this, although it can easily be done in Flash;
just draw the lightning, insert it as a graphic or movie clip into your movie, and some frames down the line press F6, then make sure that on the last frame the Alpha value is set to zero, and make a tween inbetween.
Hope this answers your question!