They will consider this as SPAM and they will refuse to index heavily tiny texted web pages. When you design you web page, it is a good design choice to add comments in your HTML file. These comments will not visible for your web site visitor. It is mainly for your ease of maintaining your web page and some search engine use these comments to index your web site. You must also add a text description for all your graphics that you use.
Some search engines are case sensitive.
Let say you did every thing right and added all the keywords, ALT, comments, etc. You need to create informative content for your web site to encourage people to come more that once and visit your web site. In long run, a solid web site respecting different search engine criteria along with a solid content, will help you to build more traffic to your web site. Once A Month You should submit your web site once a month to major search engines. This is considered to be Spamming.