A (very) Brief History of the Icthus symbol
The word Icthus is Greek for "fish" - ichthyology is the study of fish.
During the age of the Roman empire, the people who believed or put their faith in Jesus were strongly persecuted. Neither the Jewish priests nor the Roman soldiers liked this new religion, because they believed it to be in conflict with their authority. Many of the "people of faith" were in danger of being arrested or tortured if they were discovered as being followers of this man who claimed to be the Son of God and was perceived as wanting to overthrow the government. Because of this, they had to meet secretly. The reason these followers of Jesus used a symbol of the fish is shown below.
Matthew 4 (NIV)
It was common practice for people of the day, while they were conversing with someone on the street, to stoop down and draw in the dirt - much like we use our hands to gesture. If someone suspected they were talking with another person of like belief, they might draw an arc in the dirt. If the other person was a believer, they would complete the stylistic fish representation by drawing an adjacent, intersecting arc. This way, they could acknowledge each other without risking being seen or overheard by the authorities. Many believers would draw an icthus on the doorpost of their meeting place to let other believers know it was safe to meet there for worship or study.
As you may have already concluded, I am also a believer in Jesus as the Messiah - the Son of God who died by crucifixion, and was physically raised from the dead. I believe this happened so he could take my failures on himself to pay the penalty for my sin, and also to give me a new life and spirit so that I would live with him forever in paradise. I do not wish to force my beliefs on anyone, but I put the "fish" symbol on my website to let other believers know where I stand. At the same time, I also acknowledge that it is not my right or privilege to share this information with everyone, but rather that it is my duty to share the truth about my Savior with anyone who will take the time to listen to (or read) my words.
If you would like to find out more about why I believe the way I do, or would like more information about living a life free from worry about the future, I would be more than happy to converse with you about my beliefs. I have no desire to argue with anyone about religion or semantics, but I will give you the best answer I can if you have any questions of me. If you disagree with my right to believe this way, remember you also have the right to believe as you wish. I will not argue about this.
Here are a few resources on the net for further study or enjoyment: