Employers are using as many tools as possible to screen potential hires. This means that many even look up profiles to see who you really are. Have you Googled yourself? Looked at your Facebook or Twitter account to see what impression a potential employer might draw? You should.
An employer once told me that they were on the verge of hiring one of our students...until they saw their Facebook account. There were several posts degrading the student's present place of employment and the student's co-workers. Would you hire someone that spoke poorly of your business and employees? Neither would they.
Always know what information is available on-line about you. The employer should not be the first to know!
