It is not possible to accidentally bid on an item. Here is a link you can have a look at telling you about times and reasons which are and are not acceptable for retracting. There is a Bid Retraction form near the bottom you can use:
http://pages.ebay.ca/help/buy/questions/retract-bid.html
You can also ask the seller to 'unbid' you, but the seller does not have to do it, and would most certainly add you to her list of blocked bidders, -- if not for retracting then for fibbing. 🙂
Retracting is considered poor form, and as such the number of times you do it is displayed on your feedback page. Too many could result in sanctions from ebay. Not to worry, everyone does it when they're new. Just don't make a habit of it.
Instead, - when you see something you like, about a half inch below the bid button is the phrase Add to watch list. Click that, and it adds the item to your personal Watch, which you can access from the My eBay at the top of the page, or the left column. That way, you can ogle the items, price compare, and wait until the last minute and you are reaaaalllly sure you want it.
Good luck. 🙂
