How to make Chrome extension with button, popup, quick search results?

I want to make a Chrome extension.
It should have a button on side of address bar.
When we click on button there should be a small popup where we can search something quickly on 2-3 websites (like e-commerce sites).
When we click on any search result it takes us to corresponding website.

Automatically adding an icon to all PDF extensions (when any link points to a PDF file)

I am a CSS amateur, using wordpress. Someone set up my stylesheet to automatically put a PDF icon next to links pointing to any file ending in .pdf, which looked like this:

a [href $='.pdf'] {
padding-left: 18px;
background: transparent url(../images/pdf.gif) no-repeat center left;

The above code works nicely, so on my document archive page, for example, I use an ordinary <a href="anyfilename.pdf"> and the icon appears to the left of the link, as I want it to.

Syndicate content