Not immediately, unfortunately this can happen without warning as the SEC does not first send out a warning before a halt (usually based on fraud). For a good case of this - check out CSHD (CSHD.pk).
As far as delisting - there can be a few reasons for this to happen -i.e. - not filing the financial statements in time (10k, 10K-SB, 10Q, 10Q-SB). The ticker symbol will then get an 'E' appended to the symbol. Again, this happened with CSHD. For about two weeks the symbol was CSHDE due to their inability to file a 10K. To get around this, they can file an NT-10k which is a request for an extension to file the financials... if you research CSHD again (Search SEC.gov for the company Furia) you will see all of this. Great example of a company that everything went wrong with. lol.
If the stock is delisted, I don't believe you can get your money back. Not from the stock market anyhow - other means may be possible with the help of legal aid - but that's neither here nor there and it's not a guarantee. I'm not recommending it, rather, just shedding light on the subject. Now, I'm not an expert at all this, but have been through it in a real experience (CSHD lol) and learned the hard way. Just be wary of Pump and Dump schemes... use Charting and technical analysis to help you in choosing a stock. Use this board as it's a great resource. And always - *ALWAYS* - take your initial investment out if you are up on a stock pick. Heck, maybe even take a lil more than the initial. CSHD increased 400% and you could have easily sold some shares to recoup your initial buy-in and ride free shares to the moon or to the dirt!!! lol, hopefully the moon. Hope that helped.
Are you new to trading and/or pennies?