I work for a client for a few hours a week as a freelance web developer. I'm a mid level developer, but sometimes I make easy stupid mistakes, like spending around 35mins wondering why the addon I created is not working and start debugging to find out I didn't activate it in the first place. should I charge on easy stupid mistakes like that?
Delays which are due to your business/working practices are typically not the clients responsibility.
Let's look at the situation with a similar scenario.....
You're working along on a client's project and mistakenly close a file without saving it. Silly error, but I'm sure it's happened to most. This error means you have to redo what you just did for the past hour. That's an additional hour of your time.
If something, in the middle of a client's project, incurs time not directly related to the completion of the project, then it should not be invoiced. If I made some silly oversight which adds significant time to working hours in order to correct, I wouldn't feel right invoicing the client for time spent correcting my oversight. I'd not invoice for time spent on my error.
I couldn't help but had to leave my own insights on this matter as I am seeing two of those previous answers are all implying a client shouldn't be charged for his employee's mistakes.
If this question is about the rights of getting paid when the delays have been made due to freelancer's inexperience, low-level skills, or working practices - as opposed to his/her hidden features like characteristics, inattentiveness, or negligence - the client still has to pay for it. Errors and mistakes happen everywhere, every time. There's nothing guilty about it.
The reason is clear: The client shouldn't have hired his employee in the first place if his/her skills didn't meet up his expectations. That's what employers do. And most importantly, he should be responsible for his choice of choosing whom he is working with, and what his employee's mindset looks like.
Refusing to pay for the mistakes can only happen when the client thinks he has hired a working robot, not a human. Otherwise, any hours spent on the work that is related to the client's project are subject to the regular payment, especially when you are working on an hourly basis.
As long as you have materials that support your claim you didn't idly spend time for those 35 mins, you have full rights to get paid.