Outdated information on the website is the ninth mistake in the original top 10 usability mistakes in web design list by Jakob Nielsen (1996). Some twenty years ago you might happily read a dictionary that was already ten years old, but nowadays web denizens want fresh, reliable and accurate information. If some pages in your website were last updated year or two years ago, your users will start asking questions and will wonder if these pages (or the wholes site) is still being maintained and if your site is reliable or not. Worst still, there might be some old and now false contact or price information still left in some distant corner of your website and no there is no doubt that some of your users will find those and then you might wonder why some of your customers (aka users) are furious that they cannot contact you or because price was higher than expected or certain item they wanted isn't available any more though some web page said otherwise.
This mistake is still as valid ( and maybe even more so than before) as it was before, so don't just keep on creating new content but stop to do some pruning to your site from time to time and try to find and update or remove all traces of old information. And if you have a habit of sprinkling the same information all over the website in different pages, it will not only be a nightmare to update that information when necessary but you will certainly forget to update some of the places, much to the chargin of your users.