a general tax on employers.
As employers are already taxed, I'm assuming you mean an additional tax.
So, you tax an employer, here are his options:
1. Hire fewer employees ... putting more people on unemployment benefits
2. Raise the price of his goods or services ... making the minimum wage / unemployment benefits worth less
3. Keep the existing number of employees and paying them less ... meaning his best employees will leave and the quality of his goods and services (for which he now has to charge more) will decrease.
4. Go out of business
5. Take the hit and explain to his existing or potential investors (including the banks which give him operating credit) that their investment will now have less return than before and hope they will be understanding -- given that most investors have employees of their own, this reduction in ROI will only compound the same issues into a cascade effect.
In the mean time, we're paying people to stay home and watch reality TV because there are fewer jobs in the free market.