Hi:
For starters, HTML and CSS are not programming languages. One is a markup language (used to add meaning/metadata to text) and CSS is styling language based upon a set of rules.
Ultimately, if you can connect to a socket with it, you're able to work with it in LFS. Now, with the languages that you specified that you are familiar with, your options are as follows.
As for using with LFS, there is PRISM, which is for creating InSim utilities in PHP. This does requires a knowledge of Object Oriented Programming in PHP.
The other (unstable) option is XI4N, which is JavaScript, but requires strong knowledge of JavaScript, particularly in NodeJS. It doesn't give you any real high-level interfaces to LFS's InSim data, but I have found it invaluable in my own development. It does require a high-functioning ability in JavaScript currently.
The other, more popular option is to use InSimDotNet, which requires either C# or VB.net. Most people use it with C#, so documentation on using it with VB.Net may be scarce.
I don't want to sound rude or presumptuous, but I believe that an InSim application may be at a level that's above you. Feel free to prove me wrong, but the level of difficulty is rather high as there's a lot that one needs to learn, most of which isn't learned in the overall course of Web Development (which I gather your skillset is in).