ASP vs PHP Specifics ?

Hello,

 If you can please give answers to as many of these questions as you can.

 I use asp sometimes, but never php.  I want to know would it be better to

begin a new site with asp or php this time? why?

 1. Access is limited to 2 gigabytes (GB), and is limited to 255
concurrent 
users as adobe do***ent says.  Does concurrent mean exactly at the same
time? 
Meaning 255 users on the same website searching for the same word or
different 
words? Meaning that if I have 300 visitors at the same minute searching
through 
a search box or text links the system will lock up?  Big question is -->
What 
would I expect to be my limited number of unique visitors per month with
MS 
Access & ASP?? anyone have experience with that?

 2. How is MySQL interface different or similar to MS Access? Is it
simple?

 2. How big is the learning curve going from asp (Access) to php (MySQL)
within 
Dreamweaver ?

 thanks for all this, I figured a couple days of responses will save me
months 
of time..