Most etiquette experts will tell you that sending wedding invitations online "just isn't done" and most couples (and their parents) will agree.  As far back and one can remember, wedding invitations have been sent by postal mail (aka snail mail).  As a general rule, wedding invitations should ALWAYS be sent by "snail mail" and this is how most couples will choose to send their invitations.  However, with that being said, some couples may choose to send their wedding invitations by e-mail or by using e-vites.  Also, there are some that will send the actual wedding invitations by postal mail yet send additional invites online.  These might include bridal shower invitations, rehearsal dinner invitations, or save the date cards.

If  you are a non-traditional couple or  possibly planning a very green wedding, you may be considering using online invitations for your wedding, shower, rehearsal dinner and any other wedding related events.  When sending online invitations there are still a few guidelines that should be followed.   

As little as five years ago most couples would have cringed at the suggestion of sending online wedding invitations.  Many of the older relatives didn't even have e-mail or access to the internet.  Also, the thought of someone opening an e-vite with a dancing pickle inviting them to the wedding just wasn't something most people would consider "wedding worthy".  However, things have changed drastically over the years. Just about everyone has internet access and an e-mail address and many people are on Facebook and Twitter.  This makes online invitations much more practical.  Things have changed quite a bit in the design of online invitations as well.  There are now some beautiful options that might even rival a traditional paper invitation.  

With all that being said, there are still some couples that will not want to break with tradition yet still want to have an eco-friendly wedding.  You can compromise.  Send the formal wedding invitations by postal mail, but send the save the dates and invitations to all other wedding related activities by e-vite.  This is a good compromise that allows you to adhere to tradition for yourselves or your parents yet still make an effort to be environmentally friendly.  There should be one notable exception...thank you notes. Thank you notes should still be very personal and sent by postal mail.  They don't have to be elaborate or even have an envelope.  You can just send a nice note on a postcard, but it should be personal and sent by snail mail.