The first one is applicable to all forms of chess, many players will offer a draw when they feel that their position is worsening. One strategy to counter this is to always ask yourself, "Why do they think their position is worse?", when you are offered a draw.
The 2nd is peculiar to the internet, as in OTB, a blunder is usually followed by some exclamation, usually rude :) and resignation. My personal feelings are that mouseslips are just part of the game, you'll win some, you'll lose some because of them, so unless it is an opponent I know and trust, mouseslip equals blunder, live with it.
A couple of 'tactics' I've noticed becoming more prevalent on Live Chess that players may want to be aware of:
1. Beware the draw offer when you're winning the game. People unfamiliar with live chess may click without reading. Make sure you read everything thoroughly before you click it. Some will offer a draw just before you mate them in the hopes you will accidentally click the accept button.
2. "Oops, my mouse slipped." While this may be true, it may also be true they simply blundered. Blunders happen much more often in Live Chess than in the other formats. At least they do for me. However, I've noticed a good 50% of blunders made by my opponents are due to a 'skipping' or 'slipping' mouse. Use your judgement on this one and DON'T be bullied by someone trying to use guilt as leverage on you.
For the most part, Live Chess is a lot of fun and the players are fine. I'm sure the above will be familiar to some and probably unfamiliar to others. Personally, I've noticed both happening more often and thought I'd call some attention to it.