Dear Kristyna,
I don't have any experience with AddThis widget, but I know a little bit about html, css, js and a couple of other backend technologies, which I use everyday at my work :).
I am trying to build a reputation here starting with small projects in hope to make my way up :). I would like to ask you kindly to give me link to your site in order to see if I'd be able quickly in an hour to help you out. I'm willing to go further I'll see what I can do and I will write you back with my solution, than if you'd like you'd be able to fix it yourself and forget about me, or award it to me and increase a little bit my reviews :) OR I will see that because of not knowing this widget I wouldn't be able to fix it quick and you'll choose someone else. Deal? :)
Beset wishes,
Nikita
P.S. As I work in a company making corporate software I can not show you my work, but here:
[login to view URL] you can find some old code with different exercises. Also in my profile here there is a link to one javascript demo game with physics simulations.