Thanks for your comments. Actually, a while back I did in fact read the online instructions regarding using child themes. However, there must be something that I am not quite grasping, because when I attempted to do so, it broke my blog. I started getting all kinds of errors.
I just re-read the instructions for creating a child theme and tried again.
This time I made an exact copy of my current already-altered TwentyTen theme, and I renamed the folder "twentyten-child".
I made sure that I have "Template: twentyten" in the head section, as well as "@import url("../twentyten/rtl.css");" after the head section, and before all of the CSS code.
After that, when I try to activate my child theme, I start getting errors like this:
Fatal error: Cannot redeclare twentyten_excerpt_length() (previously declared in /Applications/myServer/mySite/Blog/wp-content/themes/twentyten-child/functions.php:231) in /Applications/myServer/mySite/Blog/wp-content/themes/twentyten/functions.php on line 231
In the "functions.php" file -- which that error is talking about -- there are all kinds of comments like the following, and I am not sure how I am so supposed to do what it says:
* To override this in a child theme, remove the filter and optionally add
* your own function tied to the wp_page_menu_args filter hook.
If I try to fix it with my limited understanding, then my server just throws me a similar error with the very next function, and on and on it goes.
That is why I gave up. I just couldn't figure out what I was supposed to do.
In other words, am I supposed to remove the entire function from the child's "function.php" file, or just comment it out? Do I need to then write another function to replace it?
I don't know PHP, and usually just alter the actual HTML and CSS in files. I don't know how to write functions.
Any assistance would be greatly appreciated, because the online instructions don't suffice; at least not for someone at my level of understanding.