AdWords, MSN, and a number of other platforms all contain opportunities for users to set the budgets at both the account level and the daily (or monthly, for MSN) level. Take advantage of these opportunities. They are a great safeguard to make sure that you don’t spend more than you intended. Beware though – Google can exceed a daily budget by up to 25% without owing any credits back to your account. Therefore, if you are on an extremely tight budget, set your budgets a little bit below what you can spend to be sure that you don’t go over budget.
If you have a budget set at the account level, you will not be allowed to spend more money than that budget. Therefore, use account level budgets as a last safeguard to ensure that you never exceed your advertising budget.
Not on a tight budget? Set account level budgets anyway at the highest point of what you can spend – that way in case a mistake is made somewhere along the line, you will still never owe more than your budget cap.