This article tells how to clear history and cache from Mozilla Firefox. You can use the shortcut keyboard or with Mozilla Interface

I. Using Alternatif Button

Step 1. Press button Ctrl + Shift + Del

Time range to clear "everything", and "Clear Now"

II. Using Firefox Interface

Step 1. Click button on right top side panel Mozzila,  and choose "Options".

Step 2. Select Privacy & Security - cookies and Site Data - Clear data

Step 3. Tick as this image below "Clear"

III. Refresh Firefox

Step 1. Click button on right top side panel Mozzila, click button "Help", and click "troubleshooting information"

Step 2. Click refresh Firefox, and click Finish 

Note : if you use step 2, your setup printer margin will be back to default. If you want setup it back, you can use this following article : https://support.dealpos.com/hc/en-us/articles/115001462827-Setting-Up-Margin-Printer-on-Browser

Video For SELL Page Error When Open In Mozilla Firefox (Clear Cahce)