I currently sell items on ebay, and my supplier has their own website that I get my items from to sell. What I'm planning on doing is opening my own website to sell these items instead of using ebay, but the thing is I don't have an inventory of these items (I usually sell the item on ebay, and pick them up the next day from my supplier to ship them out). I was wondering if it's possible for my website to somehow connect to my supplier's website to see if the item is in stock, and if it is not in stock it would not allow the customer to purchase the product (by saying "Out of stock" or something like that). I'm a complete beginner to any of this. All I know is simple HTML so I apologize if this request is unrealistic...any help would be appreciated.

Can be done, if your supplier has some kind of api in place which you can use to connect to your suppliers inventory system and find out current inventory status. It can also be done using screen scraping but that depends on whether your supplier shows inventory status on his website or not. You'd have to use a programming language to do this, can't be done using just HTML.

They would have to give you access to their database. Unless you can do like dman said and write a program to search on their web page and then parse the results.

Most drop shippers have some way for a seller to check their inventory.
Using the supplier database for the products is not a good idea as you end up displaying the "boilerplate" text which is duplicated on other sites using the same products.
All you need to do is make a call to the supplier Db to check stock as the page is requested.

chrishirst...you may be correct about that. I will be asking them soon to avoid all the hassle of scraping. BUT, if I am forced to screen scrape, there is 1 problem I am running into. My supplier's website requires us to log in before we can even view the page of the item's information. Is there a way around this?

It would make it a little more difficult but that is really a server side code issue not a database question.