Have you already posted about this issue? If so, DO NOT POST a duplicate. Instead, reply to your existing post, with MORE information.
What version of Zen Cart are you using?
Has your site been upgraded? When? From what version(s)?
If you've upgraded, HOW did you upgrade? (official upgrade procedure or an automated script from your hosting company?)
What addons have you installed? When?
HOW did you install it? (upload via FTP and run zc_install, or a one-click install from your hosting company? (one-click installs are NOT recommended))
In what ways is your site customized or different from a brand new uncustomized install?
If you're encountering display/layout problems, post your site URL* so it can be seen in action.
If you're encountering problems that could be related to your server or hosting company, include the name of your hosting company (not their URL).
HAVE YOU LOOKED IN THE FAQ AREA for answers to your question? (ie: a search for your error message or what you want to edit/change, etc)
Have you searched the FORUM for your error message or for answers to the question you're asking?
WHEN did the problem "start"? How does that compare with other events of your hosting company, changes you've made to your site files/addons, or your admin settings, etc?
If this is your first store, have you tested all aspects of transactions before going live?