Certain websites don't work in Ubuntu Firefox

mmm they work for me
it seems related to flash. Are you sure you installed the flash-plugin properly?

please open a terminal and type this

sudo dpkg -l |grep flash

and then paste the result

I got the following when typed sudo dpkg -l |grep flash in the terminal

ii adobe-flashplugin 10.0.22.87-1 Adobe Flash Player plugin version 10
ii flashplugin-installer 10.0.22.87ubuntu2 Adobe Flash Player plugin installer

When you launch Firefox from the terminal is there any output while visiting those sites?

How do I launch from the terminal? I usually just click the Firefox icon on the toolbar on the top of the screen.

press [ALT]+[F2] and type:

gnome-terminal

(or you can go Applications -> Accessory -> Terminal)

and then in that terminal:

firefox

Still the same results for all three sites. Maybe its an Ubuntu setting I need to change.

OK...

get:

about:plugins

in the address-bar and look there what you find about "java" and "flash" please.

When you launch the firefox via terminal there in the terminal could appear some error messages that you usually don't see when you lunch the application the usual way.
So when you visit those sites you just look in the terminal from which you launched FireFox to see if there are error messages. You can copy them and paste in your answer here.
Note if you close the terminal the application launched in it will terminate too.

I found nothing about java when I put about:plugins in the address-bar. But had the following about flash.

    File name: libswfdecmozilla.so
    Shockwave Flash 9.0 r999

I launched Firefox from the terminal but nothing showed up in the terminal.

I also restarted Ubuntu and from the grub menu chose the recovery version and all the websites work fine. i think something I have installed or set is causing the trouble. Any ideas on that?

please try this

close every firefox running. open a terminal and type (watch at the dots!) :
mv .mozilla .mozillaold

and than start firefox. don't worry if you can't find you bookmarks.

I tried that and the sites still don't work right.

When I restarted in the grub menu I arrowed down to Fiesty fawn kernal 2.6.20-16-generic and 2 of the 3 sites work. I normally choose the first option jaunty kernal 2.6.28-13-generic. Any ideas on why an older version works better than the new?

the situation is a unclear:
did u install a clean 9.04 or did you update from a previous version?
may you paste here the output of the following command?

cat /boot/grub/menu.lst

I mean the part between
## ## End Default Options ##

and

### END DEBIAN AUTOMAGIC KERNELS LIST

I did an update.

here is what I got from cat /boot/grub/menu.lst command

# This entry automatically added by the Debian installer for an existing
# linux installation on /dev/sda2.
title Ubuntu, kernel 2.6.20-15-generic (on /dev/sda2)
root (hd0,1)
kernel /boot/vmlinuz-2.6.20-15-generic root=UUID=5fa27c4d-73fb-4e77-b3df-04dbbe39a0ed ro quiet splash
initrd /boot/initrd.img-2.6.20-15-generic
savedefault
boot

# This entry automatically added by the Debian installer for an existing
# linux installation on /dev/sda2.
title Ubuntu, kernel 2.6.20-15-generic (recovery mode) (on /dev/sda2)
root (hd0,1)
kernel /boot/vmlinuz-2.6.20-15-generic root=UUID=5fa27c4d-73fb-4e77-b3df-04dbbe39a0ed ro single
initrd /boot/initrd.img-2.6.20-15-generic
savedefault
boot

# This entry automatically added by the Debian installer for an existing
# linux installation on /dev/sda2.
title Ubuntu, memtest86+ (on /dev/sda2)
root (hd0,1)
kernel /boot/memtest86+.bin
savedefault
boot

- did you upgrade from feisty to 9.04?
- in the previous message you wrote that you pick 2.6.20-16-generic instead of 2.6.28-13-generic are you sure? do you still see those menu items when you boot your machine? I ask this because in your menu.lst I can only see 2.6.20-15-generic.

something weird here

Actually now that I think about it when the new version came out I split the same partion 24 gb total 10 gb for 7.04 and 14 gb for 8.04 I just upgraded the 8.04 to 9.04. hope this sheds some light on things.

Yes I still see those menu items in the grub menu.

Thanks Damiano Venturin, that solved my question.