Are these 'not found' errors a concern?

[nicole.healthline]

Our webmaster report is showing thousands of 'not found' errors for links that show up in javascript code.

Is this something we should be concerned about? Especially since there are so many?

[anthonytjm]

Are they internal missing links or external missing links?

If internal, then that would be a big problem.You can click on the link that will show you three options. Error details, in sitemap or linked from. Make sure none are from sitemap.

If external, not so much a problem because it would be beyond your control as to who is trying to link to your site. My webmaster tools show missing links all the time from outside sources we have nothing to do with. I usually just contact the source and ask them to remove the link, or if its from a semi quality site Ill ask them to fix the link and give them the accurate url.

I would make sure you have a 404 error page setup for any bad urls linking to your site. Hope this helps.