There are many tools. The one you choose is up to you. If you are just starting out with HTMl I would suggest NVU.
W3C Amaya
Amaya is a complete online web browsing and authoring environment and comes equipped with a WYSIWYG style of interface, similar to that of the most popular commercial browsers. With such an interface, users do not need to know the HTML or CSS languages.
NVU
NVU (pronounced N-view, for a "new view") makes managing a web site a snap.Now anyone can create web pages and manage a website with no technical expertise or knowledge of HTML.
Quanta Plus
Quanta Plus is a web development tool for the GNU/Linux K Desktop Environment. Quanta is designed for quick web development and is rapidly becoming a mature editor with a number of great features and lies at the heart of the KDE Web Dev suite of tools.
Bluefish
Bluefish is a powerful editor for experienced web designers and programmers.Bluefish supports many programming and markup languages, but it focuses on editing dynamic and interactive websites.
OpenOffice Webwriter
OOWeb is a WYSIWYG web site design tool, part of the OpenOffice suite. It has features very similar to that of Microsoft's FrontPage.
Mozilla Composer
Mozilla's(Seamonkey) HTML editor keeps getting better with dynamic image and table resizing, quick insert and delete of table cells, improved CSS support, and support for positioned layers. For all your simple documents and website projects, Composer is all you need.
SciTE
SciTE is a GUI-based single-document editor which uses the Scintilla editor component. It rapidly styles most common programming languages with good control over how syntactic elements are displayed, and features folding for C++, C, Java, JavaScript, and Python. Styling of HTML also styles embedded scripts written in VBScript, Javascript, or Python.
SCREEM
SCREEM is a web development environment. It's purpose is to increase productivity when constructing a site, by providing quick access to commonly used features. While it is written for use with the GNOME desktop environment in mind it does not specifically require you to be running it, just have the libraries installed.
