Mich Robinson wrote:Are these techniques common?
ie would most browsers support them?
What happens if they're not supported? ..
The answer to each question is 'it depends on the technique you are referring to'. I am not about to write a treaties covering all possibilities. Be more specific and put some research in, before I'll offer any more.
Mich Robinson wrote:..PS I don't have any control over user's browsers.
And that is a good thing. If web/server side developers start thinking they have any right or power to control the user or their browser, things go down hill rapidly.