You're asking about "textspeak/chatspeak" or "sms-ese". Well, it came about from limitations of space (sms allowed only 160 characters) or time (the speed of online chat). Twitter allows only 140 characters, so in these cases there is a "need" to condense the language. However, if a person uses this style out of context (chat/sms/twitter), such as in regular emails or on websites in general, then it makes the writer look stupid or ignorant. I'd think you were a bored teenager trying to impress his or her friends. This is a very big nuance! :D Even among my closest and most casual friends, we don't really use this style. However, that's just us. If your (native English) friends are comfortable with using textspeak with you, then of course feel free to reply in the same way. However, please don't think this style is generally acceptable - some English students use this style because they think it is "real" or "authentic" English, but really, it gives the opposite effect. You'll see that almost none of the native English speakers on italki write this way, unless it's for a joke. Here's a safe suggestion to follow: if you have the time and space to write something properly, then write it properly. We do appreciate people who show some care when they write! ;)

All your examples are correct. If you were being even more correct, you would write "thank-you", including the "-". The disappearance of hyphens in modern English is a bad trend, in my opinion. It is wrong not to use capital letters at the beginning of sentences in written documents, even in emails. I correct quite a few notebook entries and this is a common problem among non-native-speakers. Standards of English among native-speakers are generally on the slide, but on this point, there has been no relaxation of the rule. On mobile phones, the issue of capitals is different because you can't easily switch to capitals and the whole format is more informal. It is OK to abbreviate in almost any creative way you can imagine. e.g. "nice 2 b with u, m8" Thanks for question. All the best, Michael

Typing with lowercase letters and/or numbers is considered very informal. It usually only happens on the internet or in text messaging. Typing with uppercase letters and without numbers is more formal.