Scam sites which collect your payment but then do not deliver products.
Websites which will sell chemicals mislabelled as genuine research chemicals, with the potential for disastrous consequences.
Websites which sell genuine chemicals whenever they've supply however when they don't have supply they deliberately mis-label then sell other chemicals as genuine research chemicals.
In navigating the minefield of sellers there are a variety of precautions that the research chemical enthusiast who is seeking to buy something should stick to:-
1. Take note of friend's recommendations (but be skeptical of tips about forums unless substantiated by other forum members also).
2. Does the web site look 'clean' and professional? It might sound obvious but a reputable and professional seller should have an internet site that reflects these very traits. May be the site regularly updated?
3. Be wary of sellers offering products which no other seller has the capacity to offer at that moment in time.
4. Does the seller display a complete set terms and conditions on their website?
5. Does the seller use a respected 3rd party payment processor who uses SSL encryption to process your card details? Check in the address bar from the page on which you're to submit your payment details the website starts with 'https' and never 'http'.
6. What are the hidden costs? Check to see when the vendor charges a fee for this this is not excessive.
7. With regard to the particular quality of the seller's product, this is nearly impossible to determine simply from looking at their website. Is the seller selling a well-known branded product? If that's the case, the study chemical buyer might take some re-assurance from this. The point is it might be wise for the buyer to create a small 'test' purchase when buying from a particular seller for the first time, before placing any larger orders.