Sometimes Gmail may be loading painfully slow for you, or defaults to the slower HTML mode for users. If you do not want Gmail to make the decision on which type of UI it should load for you, here is a list of Gmail modes you can use with Gmail, thanks to Alex Chitu from Google Operating System.
Safe Mode Disable all the Labs features. http://mail.google.com/mail/?labs=0
Secure Mode Encrypts to and fro traffic from Gmail. https://mail.google.com/
Older Version Don’t like the newer heavier version, switch back to old UI. http://mail.google.com/mail/?ui=1
Basic Mode The plain old HTML mode. http://mail.google.com/mail/?ui=html
iPhone Mode Improvised mobile version for iPhone and Webkit based browser. http://mail.google.com/mail/x/gdlakb-/gp/
iGoogle Gadget Gadget for viewing Gmail in iGoogle. http://www.google.com/ig/gmailmax
No Browser Check Mode Got a fancy browser that Gmail does not support yet, try this URL to bypass all the browser checks in place. http://mail.google.com/mail?nocheckbrowser