Letter of the week: They should know better

Regarding the misspelt sign in last week’s Advertiser (“Access to ‘Residance’, rather than ‘Residence’ Only”), I have been noticing spelling mistakes and grammatical errors on official signs, notices and adverts for a long time now. For example: “Do You Want To Loose “(Lose) Weight?” “Ever Considered A Carer (Career) In Sales?” “Emergancy (Emergency) Exit Only”. 
The words in brackets are the correct spellings. Rogue apostrophes are absolutely rife. For example: ‘Do Not Load In Parking Area’s”. Even a teacher at my daughter’s school wrote on the board: “How many cake’s are left?” during a maths lesson. Just how was he therefore able to qualify as a teacher? The word “it’s” is often being used in the possessive sense, for example: “The dog fetched it’s ( not its) bone.” Surely everyone should know that “it’s” written with an apostrophe is only ever used as a shortened version of “it is”. I learned this at school years ago!
Yes, English grammar and spelling can be very difficult to learn and we all make mistakes. But the fact is, these mistakes are very often on official signs and adverts, produced, I assume, by people who make a living out of doing so, and therefore really ought to know better. Surely it can’t be too difficult to check the correct spelling in a dictionary. I also can’t understand how their work has been passed, and then accepted, by those who requested it.
I’m the first to admit I am hopeless at maths and terrified of computers. Consequently, the only work I can find these days is as an office cleaner. But there are times, when noticing all these howlers, that I can help feeling that myself, and obviously many others, are definitely in the wrong job!

Rebecca Culling

Hadfield Close, Clifton