I made some changes in 'SIMPLE' theme template file and I am started getting

[User Error] Uncaught InvalidArgumentException: Unable to parse string: Malformed inline YAML string ({count} {class} saved successfully.).

I am not able to locate where is the actual problem is. Please help me to resolve this issue
here is screenshot of my error page

It's a YAML parse error. Did you make any changes to the yaml files in _config/?

No, here is my current code in _config/config.yml

---
Name: mysite
After:
  - 'framework/*'
  - 'cms/*'
---
# YAML configuration for SilverStripe
# See http://doc.silverstripe.org/framework/en/topics/configuration
# Caution: Indentation through two spaces, not tabs
SSViewer:
  theme: 'simple'

is there any thing related to 'gridfield-bulk-editing-tools'

Yes. There's was at one time a bug in that module. It contained an invalid YAML string. Ensure that the lang/en.yaml file in there looks like this: https://github.com/colymba/GridFieldBulkEditingTools/blob/master/lang/en.yml

e.g. the string needs to be escaped with quotes.

## Good:
SAVE_RESULT_TEXT: '{count} {class} saved successfully.'

## Bad:
SAVE_RESULT_TEXT: {count} {class} saved successfully.

Yes, now it's work... thanks UncleCheese