Spread Firefox has been retired, so there's no need to link to it in the side bar.
See
https://wiki.mozilla.org/Spreadfirefox. Even the site that talks about the retirement of Spread Firefox has been retired.
While you're changing the sidebar, you might want to make the other links HTTPS as applicable.
Also, you might want to add an SPF TXT DNS record or something to help authenticate your outgoing email so it's not as likely to end up caught by the spam filter.
I do web sites, so if you want any help let me know.