I would like to add a 'link' to a webpage that when clicked on a mobile phone it opens a sms message to send.. (this I can do)... BUT I would like to be able to add a message or the website url within that text message and for it to already be there when the sms opens up.
This opens up a sms on my mobile... and shows the text "Send sms" on the webpage. BUT this also comes up with a page error if clicked on by anyone using a desktop...
This is going to be harder than you think, check out the SMS compatibility table on this page for various mobile browsers: [answers.oreilly.com...]
The problem with the desktop machines is there is no SMS gateway available to the browser.
You would need some SMS API service like [clickatell.com...] to send via HTML on a desktop and that'll cost you about $0.025 per message. Alternatives would be directly connecting to SMS services on your server via a POST message and some server side code which would then work whether it was mobile or not, but your site might incur those costs unless you can find a free gateway.