One you have a website built and ready to go live it is imperative that it is tested rigorously prior to the launch. Programmers are great at building websites but often you find that they are not so great at testing it, or they are a little too close to the project to test it properly. Ideally you want someone else within your company to test it and possibly a friend or family member that is using it for the first time.
If you find an issue you need to weigh up if it is something that needs to be fixed immediately and delay the live date possibly, or if it is something that can wait. If you have broken links etc, this can actually devalue your site in the eyes of Google etc so you may wish to fix them before setting the site live. Always keep in close contact with your programmer and voice any concerns you have early on to give them the opportunity to correct it.