Coder: Illustrator Infographic into a Responsive Design for Blog

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Description of requirements/features: This is not a website
Extra notes: Hello!

I'm designing an infographic in illustrator but the end result will need to be coded for the client so they can add it to their wordpress blog page.

Here's some previous examples:
http://www.vonage.co.uk/blog/setting-up-a-home-office/
http://www.vonage.co.uk/blog/small-business-trends/
http://www.vonage.co.uk/blog/anatomy-of-a-freelancer/

It looks like the previous Designer created the infographic in Illustrator, saved the background separate from the text and then coded the text ontop. Does anyone understand how it was done?

I'm not sure if saving as an SVG is going to help?

Here's the previous code:


Notice that when I say responsive - I think for the client this means that the image can be sharp on all devices and the text can be highlighted. It doesn't seem that the infographic appears on any other pages (needs to fit into that blog article width).