So many people today are using misspellings for words, like de (the), dat (that), wud (would), tot (thought), frens (friends), dun (don't) and even witchew (with you). If you must do this, please keep it to texting or instant messaging friends. However, it's not a good idea to get into the habit of using these non-words, because you may forget to spell out the words correctly when you really should.
The idea
A friend told me recently that she received a business email message written almost entirely in text language. When she replied, she told the writer that he hadn't come across very positively in his email message because it was too casual. The writer wrote back immediately in more appropriate language, and he thanked my friend very much for mentioning this. The writer had just chosen the wrong way of speaking (or writing) to my friend initially. The key is knowing when to use abbreviations and when not to.
In practice
Watch your language. When you post something on Facebook or when you send an email, your writing is going out to a much wider audience. Abbreviations such as those mentioned earlier will not give a good impression of you. In fact, they will have the opposite effect, especially if being viewed by potential employers.
It's really important that you learn to adapt you communication style depending on who you are talking to, otherwise you could end up in big trouble.