Hi Carlo, is your question about Webmaker or a different site building tool? (Your post ended up in the Firefox forum so I want to make sure it is read by the right volunteers.)

Hi jscher2000, thanks for your prompt reply. But I just wanted to know how I can open the home page of my e-shop (www.bioalgenvernichter.de) in the html mode (via the firefox browser ?) for beeing able to insert the text of the mega tag

Hi Carlo, Firefox does not include a built-in website editor.

I think you would need to either (1) use an online tool provided by your e-shop package, or by your web host, for editing files in a browser, or (2) modify the files locally and then upload them (often using an FTP client).