"Google has found malicious software may be installed onto your computer if you proceed. If you've visited this site in the past or you trust this site, it's possible that it has just recently been compromised by a hacker. You should not proceed, and perhaps try again tomorrow or go somewhere else.
We have already notified www.instructables.com that we found malware on the site. For more about the problems found on www.instructables.com, visit the Google Safe Browsing diagnostic page."
on the diagnostic page, it says;
"What is the current listing status for www.instructables.com?
Site is listed as suspicious - visiting this web site may harm your computer.
What happened when Google visited this site?
Of the 18 pages we tested on the site over the past 90 days, 0 page(s) resulted in malicious software being downloaded and installed without user consent. The last time Google visited this site was on 2012-06-16, and suspicious content was never found on this site within the past 90 days.
This site was hosted on 8 network(s) including AS4436 (AS), AS22300 (WIKIA), AS3257 (TISCALI).
Has this site acted as an intermediary resulting in further distribution of malware?
Over the past 90 days, www.instructables.com/files/orig did not appear to function as an intermediary for the infection of any sites.
Has this site hosted malware?
No, this site has not hosted malicious software over the past 90 days.
How did this happen?
In some cases, third parties can add malicious code to legitimate sites, which would cause us to show the warning message."
It goes on to suggest using the Google Webmaster tools to request a review.
It seems odd that it's always been fine before, then for no apparent reason shows this?