Review your guides at least once a year to make sure that the information is current and relevant. Link checking should be done at least twice a year.
LibGuides has a link checker that can be used to find broken urls. Once you have logged in, click on "Tools" in the top menu bar and select "Link Checker."
Alternatively, Chrome has an extension called "Broken Link Checker" that also works well. To get the extension visit: https://chrome.google.com/webstore/category/extensions and type the name of the extension into the search box. Select the extension and click "Add to Chrome." Then use the extension by click on the icon to the right of the address bar. Broken Link Checker will highlight the links it checks on the screen, and mark the broken urls in red.
At least once a year, review all published guides.