Why do we have the karpas  vegetable dipped in the salt water in the beginning of the seder? The answer to that question is that it reminds us of the millions of tears shed by our ancestors in Egypt. That’s how all our ancestors felt every single day in Egypt.  We do it in the beginning to show that we are happy to be free and not slaves. The taste of the salt water stays with us for a while. I think this reminds us how our ancestors felt the whole time in Egypt. By doing the dipping of the vegetable in the beginning we realize that even though our ancestors had that "bad taste" in their mouth, they never gave up. We have to pay attention to the details and to everything because that vegetable did not come easily to our table. We have to pray and say thanks to Hashem for creating such a beautiful fruit right from the earth’s ground. 

haggadah Section: Karpas
Source: Original/ aish.com