It doesn't seem possible, as Windows automatically opens the AutoRun menu instead of following instructions given by the stick.
Read This: Using AutoRun with a USB Flash Drive / USB stick
If you really want to add the line anyway, the command you used is the best way to open a website.
I believe the reason for Windows not automatically following the stick's instructions are to prevent malware/viruses. You could easily run a malicious program or direct the user to a malicious website. I think it's a good think that the menu comes up, you can still use the command and the user will get the option in the AutoRun Menu. You can also change the label of the stick using label=LABELHERE.
For future notice:
Try to use normal fonts & text. Not only does your "colored" font not help your case, but it may even push others away from helping you as they don't wish to deal with the customization.