Your question is very broad / not specific, but I'll take a stab.
Skinning
Are you wanting to animate 3d models? The most common approach to this is referred to as "skeletal animation," and essentially boils down to a lot of matrix multiplication. Each vertex in a model has one or more "bones" that it is influenced by, and the bones are connected to each other to form a "skeleton." Each bone has a 4x4 matrix that is used to describe its orientation relative to its parent bone. For example, an elbow bone might be the child of a shoulder bone, and the matrix of the elbow would express the elbow's orientation relative to the shoulder.
Each frame, you start with a single root node in the skeleton (perhaps the chest) and you assign the object's "world" orientation (another 4x4 matrix) to it. Then you traverse your graph of bones and multiply the bone's local orientation matrix by the parent bone's world matrix to get the bone's world matrix. This is often called the matrix palette.
Finally, each vertex in the model uses the matrices from one or more bones that it is "skinned" to to find its final location for the frame. For example, a vertex in the middle of ones leg would likely be influenced only by the leg bone, whereas a vertex near the shoulder might be influenced by two or more bones. Doing this would allow a model's arm to be raised while vertices near the shoulder would appear to "compress" (rather than fold into the upper body.)
Animation
Animation is generally achieved with keyframes in which the relative orientations of each bone are expressed. For example, an animation that depicts a model running might have a duration of 10 seconds and have keyframes every half second or so. To achieve a looping animation, the first and last keyframes can be identical. During playback of the animation, the skeleton will be "blended" between its nearest keyframes. This would have to take place before the world orientations of each bone are calculated.
Tools
There are free tools available for compiling C++, namely the Gnu Compiler Collection (GCC), as well as a free version of Microsoft Visual Studios. I'd recommend that you take advantage of a very recent version of one of these. I've been very pleased with GCC.
You might want to take a look at the video card that is available on your machine. You'll need something fairly recent to achieve some of animation techniques.
C++ and the Web
In part as a security measure, HTML is generally not capable of running native code, such as code written in C++. There are many different ways you could do 3d animation in the browser, perhaps the most interesting of which is WebGL (basically OpenGL bindings in Javascript.)
Note that there are other ways to do animation, and even skeletal animation can be achieved differently than described. For example, you can use quaternions to represent rotations instead of matrices.
