What method does a web page use to open the HTML file that you may be using as a local home page, editing the markup in favor of it's own target link in the markup instead of the one you prefer and save the file?
The permissions on my computer don't allow outsiders, people or software to alter my files.
I have a local weather page that goes directly to my locality because the former selections I made as far as state, city and zip code go are listed in the web address, so I use that target instead of going through the selection process 4 or 5 times a day.
I have noticed that the website or the browser is changing my target back to the page containing the beginning of the selection process.
I can prevent this by making that local home page to be read only, but, after updating my local home page I don't always remember to do that and then boom, my targets are changed. I think the website is doing it because Firefox really has no reason to care what the link is targeted or or would possess any motivation to change it.
Most complex websites are now using Content Management Systems for their sites. The CMS is usually PHP or Perl based and means the site is essentially dynamic. As you go through the selection process it builds the site page for you based on the input you provided. When they do that, the actual URL you go to may also be date coded for their internal tracking purposes or sometimes to prevent people from bypassing the home page of the site. Comcast.net does this with their email login page. If you save the link to it, the next day it will send you to their home page because of date coding. Even if the URL extension you see is .html the site can still be PHP based. PHP has the ability to hide it's presence as a security measure.
I hope this was helpful.