Sometimes I have seen questions with a ridiculous amount of trailing whitespace. This wouldn't bother me so much if the scrollbar wouldn't appear:
cout << "Hello World!" << endl;
It might also be that the code is indented a lot and the trailing whitespace tips the scale:
for(int i = 0; i < 10;i++) for(int j = 0; j < 10; j++) thisVariableIWillIncrementAlsoILoveCamelcase += whyNotMultiply;
It would be nice if when a language where whitespace doesn't matter is specified, trailing whitespace would be ignored.