Designer on a Windows system and saving files for a server which requires all files to have the .html extension rather than the .htm extension takes a bit of work. Otherwise, the Web. Designer to a crawl. All text entry and modification should be done before the page is formatted and the graphics are inserted. If small textual changes need to be made on a large, heavily formatted page with lots of graphics, a plain text editor should be used.
Designer comes with certain perils.
If you do attempt such an action, the program will give an error message and will crash immediately. This seems to be a special problem in the confined spaces of tables. The ability to use tables was patched into the Web. Designer editor after its original release. In my experience, the patch does not always work as it should.