Overview of ASP
ASP stands for Active Server Pages. It is a language which is used to create web applications – specifically, applications that are dynamic meaning that the content changes based on who is accessing it, what they do with the application, and the time of the day. In short, it's a language that allows interactive web pages.
ASP was one of the first scripting languages introduced on the Internet when all firms were trying to find ways to improve the web experience. In that context, it was quite a breakthrough when it was introduced and though newer technologies have sprung up, ASP is still used on a surprisingly large number of web sites – most of which were designed some time ago and see no reason to change yet. I myself am aware of several sites that still use asp.
How it works
ASP works by selectively generating the HTML based on rules coded by the programmer. This means that a .asp page (if you see it as it's being written – not as it is displayed) contains HTML code along with ASP code that dictates how the HTML is to be formed as the user is requesting it based on certain parameters. This gives the programmer fine grained control of what the user sees depending on the situation. Complex control sequences and database connectivity are built into ASP which allow programmers unlimited flexibility.
This led to what some people call "spaghetti code" with ASP control structures weaved into HTML which made things a bit difficult to read and debug.
Support for ASP
Microsoft has still kept support for classic ASP over the IIS versions. With the latest IIS 7, certain changes need to be made that will ensure that ASP keeps running. These include selecting the ASP component as it's not there by default, as well as making sure that MS Access databases can still be accessed.
IIS has also recently changed the way error messages are displayed to the user due to security concerns. Once again, these changes can be reverted back to the classic ASP defaults if needed.
By all accounts, Microsoft is slated to continue providing bug fixes and support for classic ASP for some time. Classic ASP is included in Vista, and so will at least be supported as long as Vista is supported.
Relevance of ASP today
With the recent releases of ASP.NET and sophisticated PHP 5.0, ASP is no longer actively used by a large number of people to develop new applications. BUT (and this is a big but), there are plenty of web applications currently running that are scripted on ASP.
ASP support is therefore quite crucial for these applications and your VPS host will certainly provide this support on a Windows server. This makes it easy to migrate existing classic ASP applications onto the Windows IIS 7 server without glitches. For companies that have invested a lot into a tried and tested ASP application, this can be the deciding factor when making a choice as to which hosting platform to choose. After all, why break something that works perfectly fine right now?