You Designed for Print First
The web is cheaper to change
Entrepreneurs often miss a great opportunity when starting out. They usually start by getting business cards and 5,000 flyers printed up which talk about their product or service, but they created the text in a vacuum.
After they start handing out the flyers, they realize they need to change some key copy or images, only they still have 4,500 flyers left that they're going to have to throw away.
A better approach is to build your website first. You have an opportunity to have as many people as you can grab proof your work and making changes only costs the labor. Once the copy and supporting images have been tested online, the print collateral follows.
Print and Web are different
The web is limited in what it can show. Print can use gold foil, the web can do animation, but not visa versa. Make sure your basic elements, like your logo and product imagery, will work in both places.
Be sure to keep in mind that web graphics are lower resolution than print graphics. If you want to use something from the web in print, your designer will need to create images for the website at print resolution, and then scale them down to the web.