Today while working on my another blog, I faced the problem “HTTP Error” on file uploading .
In morning, I was writing the post and require to upload some png image files. In my general practice I always optimize png files on linux system.
I did some troubleshooting and checked the web server logs. I also googled some blogs who faced this issue.
From my side I was sure, there was nothing to do with PHP related code. Most probably suspected issue was with plugins installation.
How I resolved the issue
I rechecked the .htaccess file and found some updation. The date of updated file was changed and as I know I have not changed the .htaccess file manually.
Hence, decided to revert back to previous format.
I have taken the backup of .htaccess file.
Then, login into wordpress admin Dashboard, clicked on Settingss >> Permalinks and simply clicked on Saved button
I retried uploading the file once again and it worked. Issue is resolved