using .load to load an external page fragment

using .load to load an external page fragment

I am trying to load a fragment of one of my webpages.  I am not sure if this would be the best way to do this, but thought I would try something new, and see where it gets me.  I am using .load to get part of a page, like pages.php #register.  It loads up properly, but then when you click on a button, for example, to submit the form, the whole page goes away.  I know the answer to this is probably the iframe, but I am curious if there are any ways around this, or better ways to load fragments of a page like this.  

edit:  i thought this would be a nice tool to use because it looks like it resizes the page to as big as it needs to be.