The projects you're been posting are possible to do with the web page stored in the ethernet shield SD Card ??
Yes, it is. In fact my project started out this way, only using the Arduino itself.
But there are cautions of course. With the Arduino SD card, care is needed around programing when it comes to having the same system work with ethernet. I believe the SD card system is relatively slow also, which may impact on how and what you want to do.
Keep in mind the idea that you can serve up a simple html file from the SD card and have your html code point to external resources such as fancy stuff like CSS or external libraries. Doing this will help with performance as the browser will get those files from high speed servers.
The Arduino Mega I use has onboard SD card slot as well as wiznet 5100 ethernet controller, so I simply connect it to a power supply and with a cat 5 cable, to my router.
But to remotely access your Arduino, you need to know your external IP address.
I knew the situation with mine, as it is static, it does not change over time.
Depending on your internet service provider, you may have either a static or dynamic IP assigned.
If dynamic you will need to use a service like 'no-ip', or 'dyndns' to help you with this.
Maybe your router has the provision to do this also.
Remember for remote access of any sort you will need to connect your Arduino to your ADSL/DSL router which is then connected to the internet via your ISP.
As far as the program is concerned, there are a few ways to do this, and Bill's way would be quite a suitable solution I think from what I see of Bitlash.
I will need to let Bill say if it would work with what you are wanting to do.
I would start with something very simple and build up from there.
Have the Arduino reliably read the ultrasonic signal and confirm this firstly in your serial monitor in the IDE.
Play around with this and get to know the limits and conditions under which ultrasonics will work reliably.
Then start with a section of program to present this data to a web browser if that is your intention.
I played around initially with some of the example web server programs here on the Arduino site, but I ended up using Webduino library as I really liked what it is able to do, as well as providing a good working framework that part of the software.
So, just checking, you do want to remotely view the ultrasonic level that your Arduino is reading?
And that you wish to use the Arduino to present this information as a dynamically updating html page?
If all the above is correct, can you tell us what you have done so far in terms of the program for the Arduino or are you just at the beginning stage?