I not able to find the error in this code

Tell us what’s happening:

Your code so far

// Example
function ourTrueOrFalse(isItTrue) {
  if (isItTrue) { 
    return "Yes, it's true";
  }
  return "No, it's false";
}

// Setup
function trueOrFalse(wasThatTrue) {

  // Only change code below this line.
  if (wasThatTrue==true){
    return "\"Yes,that was true\"";
  }
  
  return "\"No,that was false\"";
  // Only change code above this line.

}

// Change this value to test
trueOrFalse(true);

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36.

Link to the challenge:
https://www.freecodecamp.org/challenges/use-conditional-logic-with-if-statements

You have two issues:

  1. You are not entering the exact phrase for each return statement (missing a space).

  2. You should not be adding literal double quotes with \". The values you are returning are already strings. The extra " on both the start and end of the string is changing the value expected by the FCC tests.

thanks for your help.If could you recommend me some useful links of advanced web development it will be helpful to me

Just keep working through the FCC challenges. They will get advanced enough for you.