Why would I have so many rejected shares while mining? I am mining litecoin with give-me-coins and I have the following info on website's stats section 

 Valid Paid: 118
 Invalid (Not Paid): 113 (95.76%)


As far as I know this is not very good. 

How can I make it better ? 

I use cgminer 3.7.2 (used 3.6.6 also) with following command

cgminer --scrypt -o ltc-eu.give-me-coins.com:3333 -u user.pass -p x -I 11
You can try decreasing your intensity. Other parameters can also lower speed and decrease/remove failures. It's like running too eagerly, it might make you trip a lot.

It could also be your Internet connection or even give-me-coins itself (although I doubt it's give-me-coins itself).