hulla:Vanity bitcoin addresses are just like any other bitcoin addresses, but they are unique in a way as they contain some custom text like 1BTC............ .One just uses the private key to add the address to his wallet.
There is no additional advantage of having one, but they just look cool !
As the user uses split key generation, so there is no risk of loosing funds as he only has half the key only.
Also do not trust any site that generates the"whole" private key as they are sure to scam.
Yeah, that's what I said already. There is no risk of security in the service I provide, because only the address owner has the Private Key. I only have one Part Private Key, while im creating your address.
Just to clear the things about security up. 
Thanks and it nice to hear this words of enlightment from you guys. I will try the vanity as soon as I can in other to know how it works. Do you say it totally save?
Yes, I can say it is very, very safe,
if you download bitaddress.org HTML page and generate the Split Keys offline. Please make sure to save your Private Part Key on a secure place.Wish you a great day.
dodgrad:I can't say it like that. It depends on the difficulty. (The characters are not the only factor of the difficulty!)
Give me an example, what prefix you want and case-sensitive / case-insensitive.
Ok, lets take examples like:
1 - 6 letters after 1 - example: "1dodgra" - how much you will charge for that?
2 - 7 letters after 1 - example: "1dodgrad" - how much for that?
3 - 8 letters after 1 - example: "1korrupte" - how much?

Question - If i want change letters in this examples above - for example not "1dodgrad" but "1DodGrad" - do this will change system and price?
^^ crossed specially for @abhishek.g -> look next post.
Your examples:1.
1dodgra has a difficulty of 888.446.610.538 and would cost
0.026BTC. Final delivery in 1-5 days.
2.
1dodgrad has a difficulty of 51.529.903.411.245 and would cost
0.84BTC. Final delivery in 8-14 weeks.
3.
1DodGrad has a difficulty of 873.388.193.410 and would cost
0.023BTC. Finaly delivery in 1-5 days.
I would recommend option 3 to you, due to the price, your full name is in the address and the comparatively fast delivery.1korrupte has a difficulty of 2.988.734.397.852.220 and I would not do it because it takes 2-12 years. (The combination of this letters is very hard -> high difficulty -> high generating time. Just to explain.)
Hope you will find something that suits to you and I wish you a great day. 