When people post links on my site, I kinda want to just make sure that the website they link to is active and not dead. How can I check this?
I was thinking to use meta data or title but I don't think all sites have that.
There a lot of plugins for different languages and platforms that do this. I don't know them by name, but I'm pretty sure Django, Rails etc. have them.
That said, if you just fetch the URL people post on your and check for the 200 HTTP return code, you should be fine.
You might want to clarify your question a bit, by the way. I'm not 100% sure whether you mean people that post links ON your site or links TO your site.
You can also set up monitoring using some external service, like pingdom. The advantage of an external service is that they will hit your web site from geographically diverse clients, so, if you can't get to the site from your office, it actually may just be you.