Can we use two different Languages in one website development?

Yes,But we have to follow some rules.

add /App_Code folder to your solution .

make two sub-folders

like:

App_Code
/VB (Your sub folder name)
myClass1.vb (Your class coded in VB)

/CS (Your sub folder name)
myClass2.cs (Your Class coded in C#)

after that go to web.config file
< compilation > <codesubdirectories>compilation
< codeSubDirectories >
< add directoryName="VB" > < "/add" >
< add directoryName="CS"">""<"/add" >
< codeSubDirectories" >
&lt /compilation >
< codesubdirectories >
< add directoryname="VB" > < /add >
< add directoryname="CS" > </add >
< codesubdirectories >
< /codesubdirectories > < codesubdirectories >
< add directoryname="CS" > </add >
< codesubdirectories >
< /codesubdirectories > < compilation < > codesubdirectories > < add directoryname="VB" > < /add > < add directoryname="CS" > < /add > < codesubdirectories > </codesubdirectories >

< /codesubdirectories >
</compilation >

//Note:You are not required to name them "VB" and "CS"{Sub-folder names} as we did ,You can use whatever name tickles your fancy.