A good place to start is by reading one of those to learn about the basics of a web page (without application logic):
Then start investigating about web development frameworks and pick one that fits your way of thinking. Popular options are:
Note that there are many more options, but these seem to be the most popular.
Once you've chosen a framework (any will do, don't worry too much about choosing the best one), look at tutorials, there should be plenty about 'creating your first application'.
Once you're there, it should be fairly simple to find more information and figure out what you need to know in order to go further.
Good luck!