I had a big problems with Flash ads locking up my computer. The ads have become increasingly intrusive and annoying. They pop up, cover what your reading and at times, you can’t get rid of them. I found a hack that prevents flash movies from loading unless you tell them play. It provides a nice Click to play option on the areas of the screen displaying Flash content in Firefox. It works on most Flash movies. Here’s how you add it.

1. Find your Firefox profile folder, located at C:\Documents and Settings\username\Application Data\Mozilla\Firefox\Profiles\randomvalue\chrome

If you are using a different skin other than chrome, replace chrome with the name of the skin you are using.

2. Open the userContent-example.css (or userContent.css if it exists) file in WordPad and add the following to the end:

/* Block Flash, using a placeholder you can click to unblock a desired Flash animation. */
/* Doesn't work for embed tags, which are less common than object tags - bug 190970 */
object[classid$=":D27CDB6E-AE6D-11cf-96B8-444553540000"],
object[codebase*="swflash.cab"] {
-moz-binding: url("http://www.cs.hmc.edu/~jruderma/flash.xml#obj"); }

3. Click File > Save as… and give the file the name of userChrome.css. Close out of WordPad. You should now have a userContent.css file saved in the chrome folder.

4. Close all Firefox windows and reload them. Most Flash movies will have a Click to play option and will look like the following:

For some reason it took about 15 minutes for this change to actually work. Possibly because some data was cached. No more intrusive Flash ads