Depends on what website you'd like to build. PHP is good since it's free and there are many free source codes available. ASP is not that widely use since you'll need Windows server to run it and that is more expensive. ASP.NET and JSP have alot of cool features but I don't think they're needed for ordinary websites. For me, I'll choose to use PHP for most sites unless requirements call for other languages. Just my opinions though.
Every developer has their favorite flavor so you'll get several different valid answers to your vague question. I prefer ASP.NET and SQL Express, but I also know Ruby on Rails and PHP are great tools. It depends on a variety of factors and preferences. I'm afraid you'll need to be more specific.
In my opinion - you can't go wrong with PHP as your first preference considering how easy it is to use, how many tutorials, resources, e-books and scripts you can find on it. Second preference would have to be Ruby on Rails, you can develop websites and web applications really fast with simple code.
I've used JSP, ASP, and PHP. PHP has the lowest learning curve. You can find solutions to PHP problems easier than the other two.
English unless your website targets only people that speak a specific language. Then that language is the best language.
I think it is better to give first priority to the PHP because it takes less time, simple code and it gives good security than ASP.NET
There are many programming languages that you can choose from. It is of course impossible to choose, in an objective and absolute way the best programming language. Choosing what programming language to use is dependent on a lot of things. A programming language which may be very good for a specific use may be the wrong language to use for another task. However, I think some languages may be the best for a website are: ASP, ASP. NET, XML, Java,...