I updated my ipad to ios7 and my Targus Bluetooth keyboard does not work anymore.

That's because it's simply not powerful enough to handle ios8. I know apple gave the update but unless they give a new bug fixing update to fix the crashing, your stuck with ios8 and a crashing iPad.
I have my iPad 2 with ios7 and I'm not planning to update it.

check the manual...!
depends on the model - but it works with bluetooth- see a sample :
put the iPad in the slot built into the keyboard, and pair it with your iPad via Bluetooth
On your iPad, tap the Settings icon and then tap Bluetooth. Make sure Bluetooth is On.
Connect the Logitech Ultrathin Keyboard Cover i5 Logitech Support Article

What's your model? Processor is bigger question.

Check that the keyboard's battery is working and it's on. Turn on Bluetooth on the iPad (Settings > Bluetooth). Press the keyboard Connect button. Choose the ZAGG Keyboard on the iPad, and type the code on the keyboard.
This doc describes the process: http://cfprod.zagg.com/downloads/ZAGGfolio%20instructions/ZAGGfolio%20instructions.pdf
Good luck! :)

Once you have updated your iPad you cannot roll back the update. This is the case with iOS7 and downgrading is not supported.

Hope that helps!

Once you have updated your iPad to iOS7 you cannot remove it. Downgrading is not supported by Apple.

Hope that helps!

I suggest you let it download the updation file because usually there is no option to abort the download and if you do not want to install the update just decline the license agreement this will abort the install and you would be able to use the old version. Note: Once you have installed ios7 there is no direct downgrade available as Apple had stopped signing the previous versions.

You can update your iPad to iOS7 as long as it is and iPad 2 model or later. The update can be performed wirelessly or by connecting the iPad to a computer using iTunes.

For step-by-step directions for both methods, check out the Apple website: http://support.apple.com/kb/ht4623

Hope that helps!

Thank you!!! I held the home key and power button until the Apple logo appeared and now it connects to the key pad.