You don't. That is the job of the sysops.

I have never had to assign an IP address. My ISP always did that for me. In fact, each time my site is used, it gets a different IP address.

Just use the URL. That's all that is needed.

Many web providers are switching to randomized IP addresses, to keep spammers from hiding behind IP addresses, and to keep hackers from destroying websites.

ok, so how do I use the url only? right now if i type the url only I get a "page cannot display" message-

The DNS record needs to be changed to reflect changes in IP addresses for a given domain in any URL. If I were to type your web address into my browser now, my pc would send a dns request to my ISP's name server which will attempt to look up an IP address for that domain, if it doesn't have one it will request a higher authority dns server until it gets an address or all avenues are exhausted. The ip is returned to my computer which will promptly cache it and then send an HTTP request message to that ip address.

So if a webservers ip address is changed, if the DNS record that maps that ip to a domain name is not also updated you get the behaviour you describe.

When a dns record is updated it can take anywhere upward of 24 - 48 hours for that change to propergate across all the dns servers out on the internet. So maybe you just need to give it time.

Thanks, that sounds more like it, now how do I change the ip address for the website- the server is in house in my office and the person that was taken care of it is no longer there. how about the router I probably need to point the new ip to the internal ip right?

First of all, open a command window type nslookup press enter
type the URL www.yourdomain.com and press enter see what IP address is returned. I've attached a screen shot. Using my companies address to illustrate.

On your router NAT incoming traffic HTTP on port 80 to the internal IP of your web server.

(I'm assuming your webserver is serving on the default HTTP port which is 80)

ok but there is also cctv cameras using port 80

But they have a different IP right? external and internal.

99% of the internet is on port 80 but they all have a different IP.

right. different ip's for the cameras- one internal one external- so I should do the same for the website-after i assign the new ip to the website?

What ip did you get for nslookup? that is the ip for your web server as far as the internet is concerned. We know it's one of several ip's on the external interface of your router. So by mapping/natting (however your router works) the external ip on the router to your webservers internal ip on your private office network you are in effect 'assigning' the new ip to the website.