I want to make a free video introduction of my client's company. I just want to use images, text and little bit of effects and sound.
Is there any free web based or anything, by which I can make it?
There are several tools for editing video online. The results -however- may vary and depending of how complex is the online tool you may need to even pay to get your video downloaded.
I suggest you to run a search on google for "video editor" (with no quotation marks) in order to receive lots of online tools in a comprehensive list.
In example: This list includes 30 popular video editing online software which includes some self hosted applications to be installed in your own server like "Movie Masher", which is represented in the next screenshot.
Anyway, if you wish pro-like results, you may need to use software like Sony Vegas, Adobe Premiere, and other tools for windows. Openshot and KDEnlive are available for linux.
Good luck!