Aside from details like the who, the where, and the RSVPs, directing guests to your wedding website offers a unique occasion to share your faith with your family and friends. If you and your fiancé have chosen to create one, it's certain nearly everyone invited to your big day will visit your site as soon as they see the address online or in their Save the Date. So, consider your website your letter to family and friends--a large, and possibly varied, audience. Pray together about what message you hope to convey as you introduce your guests to who you are as a couple and to what your wedding day will be all about.
Stating why you believe what you do, in your own words and in a way that's truthful, casual, and aimed at the heart, can go a long way in making your Catholic wedding an invitation to deeper understanding and a witness to the beauty of marriage in the Church. You might consider adding any or all of these elements to your site:
Tell the story of a saint who's had a hand in your relationship.
If the Father and the communion of saints have written your love story, consider saying so. True stories of virtue and holiness speak for themselves, and they also provide an opportunity to break down why and how Catholics call upon the saints' intercession.
Include explanations of parts of the Mass, like communion and the Rite of Marriage, for guests who might be unfamiliar.
Briefly and charitably discussing modest dress in the chapel, guidelines for who can receive communion and why, and reasons the Rite of Marriage matters for the sacrament can all go a long way in making your guests--particularly non-Catholics or those who've been away from the faith--feel at ease and not experience surprises that could be misperceived as exclusive or judgmental, like a non-Catholic not being permitted to receive the Eucharist.
Host an open-invitation holy hour after your rehearsal.
One of the most treasured moments of my life was praying with my college best friend moments before her wedding rehearsal, in the chapel on our campus where we'd both, at some point, alternately smiled and wept thinking about our future husbands, babies, and marriages over the years. The tears poured down as we knelt shoulder to shoulder and as I marveled at how the Father had answered each of our hopes and prayers so specifically and abundantly in the men he gave to us.
At another wedding I was invited to, the bride and groom had their priest and a few friends help lead an hour of Adoration, confession, and Praise and Worship the night before the wedding for any guests who wished to attend. Heaven touches earth during those moments of hope and anticipation. Following suit, by planning a holy hour and sharing the details with your guests via your wedding site, is amazing for both you and your beloved and for friends and family who will share in your joy and intercede for your marriage.
Invite guests to leave their intentions on your wedding site, and pray for them.
Online guestbooks and song requests are fun, standard fare, but have you considered additionally including an Intention Box on your website for your guests? Create a page for family and friends to privately submit their prayer requests to you and your fiancé. Prayer for those you've invited to share in your day, whether they're attending or not attending, is a lovingly specific act of generosity.
I hope these ways of evangelizing to your guests sincerely call your family and friends into communion with you and express what you stand for in a loving way, particularly if there are sensitivities among them where faith is concerned.
Above all, though, I truly think the best, most important witness of all is one that doesn't even need to be typed and posted--quite simply, the joy of entering into marriage with a pure heart, radiant, evident joy, and desire for complete self-gift is impossible to ignore.
Don't worry about it being your personal responsibility to change anyone's mind about the Church. Pray for each of your guests as you address their invitations or plan your reception seating, and place them in the hands of Our Lady and her son. Be yourselves--the selves who so clearly wear their love for all to see--knowing your love flows from Love himself, and what you value and what sets your marriage apart will be crystal clear. I promise!