Q:

How to create a chrome extension to change the default tab

I would like to create a chrome extension which changes my default tab in chrome browser. 
Inside the page I will put my favorite websites, which I think I can handle using HTML + CSS. My difficult part is how to make it become a chrome extension because I have never done it before.
Can anyone give me some basic steps which I could start with?

A:

You are looking for what's called Override Pages.
An extension can declare that it supplies a new newtab page. Here's a strictly minimal manifest for it:
{
  "manifest_version": 2,
  "name": "My awesome New Tab override",
  "version": "1.0",
  "chrome_url_overrides" : {
    "newtab": "newtab.html"
  }
}

Then you can use this manifest, together with a newtab.html and required resources, to make a simple extension.
There are many guides past that point; you can see the Learn Basics part of the official docs. Remember you can always ask a new question here if you run into specific implementation questions.

