Most popular language for web developers are PHP, Perl, ASP, Java and Python. PHP and Perl are among the most popular because of the dominating of unix based web server in the world web hosting arena.
PHP and Perl are server side scripting language which you must have a copy of the software installed on the web server to run it. Java can be server side or client side depending on the version you used.
C/C++ is the most famous offline or online language platform and many program nowadays written by this language.
VB (Visual Basic) was derived from BASIC and enables the rapid application development (RAD) of graphical user interface (GUI) applications, access to databases using Data Access Objects DAO, Remote Data Objects RDO, or ActiveX Data Objects ADO, and creation of ActiveX controls and objects. Scripting languages such as VBA and VBScript are syntactically similar to Visual Basic, but perform differently. Visual Basic (VB) is a third-generation event-driven programming language and associated development environment (IDE) from Microsoft for its COM programming model. Programs written in Visual Basic can also use the Windows API, but doing so requires external function declarations.
ColdFusion is an application server and software development framework used for the development of computer software in general, and dynamic web sites in particular. In this regard, ColdFusion is a similar product to Microsoft ASP.NET, JavaServer Pages or PHP. ColdFusion was the first amongst these technologies to provide the developer the capability of creating dynamic websites that were attached to a backend database.
ASP.NET is a web application framework developed and marketed by Microsoft, that programmers can use to build dynamic web sites, web applications and web services. It was first released in January 2002 with version 1.0 of the .NET Framework, and is the successor to Microsoft's Active Server Pages (ASP) technology. ASP.NET is built on the Common Language Runtime (CLR), allowing programmers to write ASP.NET code using any supported .NET language.
For simplication, you can use ASP.NET, VB, Java and C/C++ if you are working on a Windows platform. Use PHP, Perl, Java, Python, ColdFusion and C/C++ if you are working on a unix based platform. Almost all programming language has their online/offline capability so it will depend on what kind of application and environment you wish to apply.