You may use information that you find by doing a web search but that information cannot be cut and pasted into your response unless you have the express permission from the original author. Failing to obtain permission can be a violation of someone's copyright and carries stiff civil and criminal penalties if you are caught. Supplemental information may be an asset to the customer, so you may provide links to information that you think they would find useful.  General rule of thumb - if you want to cut and paste, sum it up in your own words instead and then give the customer a link to pursue on their own.