I am making a flash website, and i was sondering if anyone has a rough guide as to how big is too big in terms of the length of time it takes to load, is there an ideal size that I should try and stay under?
When I worked at BBC online, we had a rule that no front page, (ie the first page the public goes to), should be larger than 150 kb. That was in the days before broadband (DSL) popularity. It's worth bearing in mind that broadband take-up in the UK alone is still under 20% of internet-ready homes.
From the figure of 150kb, you can extrapolate how long someone is prepared to wait for a download. BBC allowed games to be larger (because people have chosen to click on something they expect to be worth the wait), and I've been to an entire website that was one flash movie clocking in at 1.5 Mb, yet because of a very fast host server, the entire thing loaded in seconds.
For websites, I'd always provide an html version too. Some people can't install any software (including flash player) on their work PCs or may not have broadband, so won't want to wait for flash player to download.
You can always build your site in stages, so that the front page is very small, but the subsequent pages load in as separate movie clips.